


The Comparative Uses of Semaphore and Foghorns as Communication Devices in Manoeuvres Naval and Sexual

by Pyjamapants



Category: Sherlock (TV)
Genre: Exhibitionism, Explicit Language, Explicit Sexual Content, F/M, Het, M/M, Multi, Polyamory, Slash, Threesome, Threesome - F/M/M, Voyeurism, abuse of naval communication devices
Language: English
Status: Completed
Published: 2011-04-04
Updated: 2011-05-29
Packaged: 2017-10-17 14:15:59
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 6
Words: 23,133
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/177724
Author URL: https://archiveofourown.org/users/Pyjamapants/pseuds/Pyjamapants
Summary: <blockquote class="userstuff">
              <p>Sarah and John discover that inviting Sherlock Holmes into your bed requires advanced communication techniques.</p>
            </blockquote>





	1. T (Tango) "Keep clear of me; I am engaged in pair trawling."

Eight months into their relationship, John has begun some sort of informal survey of every position in the Kama Sutra with all the gusto and exhaustiveness that Sarah normally associates with his flatmate's experiments. She indulges him and the requisite interruptions required. He is _very_ thorough, after all, and they've discovered some truly enlightened arrangements as a result.

They're a couple of weeks and about forty permutations into his study, Sarah reckons, when he nudges her out of what had been a _very_ enjoyable position and directs her onto her hands and knees, telling her to clutch the footboard and promising it will be worth the interruption.

The angle is not so earth-shattering, and she's about to tell him that, really, this isn't working for her when her eyes catch on the noticeable gap between door and door frame.

They'd shut the door, she's sure of it.

"John," she begins, cut off when he licks a path up her spine that ends in a bite at the nape of her neck.

"I know," he murmurs, nipping at her earlobe. Her every nerve lights on fire and she moans.

Her eyes are riveted to the narrow sliver of hallway. The light is too dim, no matter how hard she squints, to make out anything beyond Sherlock's form lurking outside. John grips her hips harder, tighter, and she rocks back to meet each thrust.

This is... oh, God.

The position is suiting her quite well now.

Her eyes flutter shut as she shifts to balance her weight on her left hand, tucking her right between her legs. John's 'I know' is not the response of someone _just_ discovering his flatmate is a voyeur. Sherlock's done this before. More importantly, he liked what he saw enough to return. And John liked it enough not to barricade the door shut.

Just in time, she locks her elbow to keep herself from tumbling to the mattress. When she comes, it's to the mental image of Sherlock watching, stroking himself, and biting his lip to keep quiet.

When she opens her eyes, the door is closed, and she's gasping for air, John's groans filling the little room.

* * *

Sarah is thoroughly drained from her day at the surgery, but nothing could keep her away from Baker Street tonight. John had collapsed, snoring last night, and the morning had been too rushed to bring up Sherlock's little habit. And she _needs_ to talk to John about it, needs to figure out where they're going with this before the thoughts rattling around inside her head become any _more_ distracting.

She fishes her rarely used key out of her handbag, and the day's fatigue evaporates as she climbs the stairs to the flat. Her heart stutters when she sees Sherlock sprawled on the sofa, flicking through a forensics journal.

She forces herself to look away, to look at John. "Could we talk, John? Upstairs?"

Sherlock says nothing, but the corners of his mouth lift in the smallest of smiles. Oh, God. He knows that she knows – of course he does – and it's suddenly all just a bit much. John hauls himself out of his armchair, his gaze... heavy as he stalks towards the door, grabbing her hand when he walks past her.

She means to talk to John, she really does. But he's half hard before they've even got the bedroom door shut, and before she can say anything, he's kissing her towards the bed, pressing her onto the mattress and then dropping to his knees between her legs, tugging her knickers to one side before he begins kissing and licking her.

He is ravenous, and soon 'John' and 'Oh, John' seem to be the only things she can say. She tugs her skirt up, flattening it against her, so she can see him, see him looking up at her as his tongue slides across her.

Then she sees the door open, and she bites her lip. John's fingers are pressing inside her now, and he moans against her as she tightens around him.

She closes her eyes, her mind spinning images of what the view must be from the hallway, what she must look like. One of her shoes has dropped to the floor, the other still dangling from her toes. She'd kick it off, but as that leg is currently hooked over John's shoulder, it isn't really an option.

She wonders if Sherlock enjoys it more now that she and John both know he's out there watching and if he has any clue how badly she wants him to open the door the rest of the way and walk in. It's all she can do not to call out to him; she _knows_ she and John need to talk about this first or they risk being wholly unprepared for any fall-out from the decision.

But, oh, God, that crack in the door is taunting her.

She comes, arching into John's hand and mouth, her foot pressing into his back, and her lip between her teeth to stop Sherlock's name from tumbling out.

John stands, undoes his zip, and slides inside her. She wraps her legs around his waist, pulling him tighter, closer, his trousers rough against her thighs.

And then John, devilishly clever John, lowers his lips to her ear. "You're thinking about him, aren't you?" he whispers, the syllables tickling her hair.

"Yesssss," she hisses underneath him.

John's breath, already leaden, grows heavier. "Are you thinking about him inside you?" He pauses to let the words sink in, to let Sarah catch the approval implicit in the question and its tone. "Or are you thinking about him inside me?"

"Yes. Either? Both? All of the above?"

"Are you saying you're interested in –"

"Yes. God, yes."

Sarah turns her head, watching the hallway again, imagining that the door opens wider. That Sherlock walks in, trousers tented, his hand wrapping around John's hip.

She's caught in the riptide of her orgasm before that imagined hand can do anything else.

John's hips are still, his head buried in the mattress as he pants into her collarbone.

The door's shut again. John moves from between her legs and climbs onto the bed next to her, propping himself on his elbow. "So are you seriously interested in..." he trails off, clearly fumbling for polite phrasing of what it is they're contemplating.

"I am. Are you?"

John closes his eyes, and she watches him exhale. "Yes, although I'm not sure if doing this is brilliant or idiotic. We'll lose the last of the flimsy little boundaries we have with him."

She runs a finger along the buttons of his shirt, trying not to chastise John for thinking in terms of boundaries, in terms of what they'll lose instead of what they'll gain. Yes, there's quite a bit of talking to be done. "I wasn't aware we still had any boundaries. I've long given up resisting his presence in this relationship," she says, smiling. Sherlock has been there from the beginning, after all, inviting himself along, providing commentary, untying her and reassuring her when her first kidnapping experience ended. She feels stupid that it's taken him skulking in the hallway for her to see that he belongs with them.

She undoes the bottom three buttons of John's shirt, slipping her hand around his waist.

John smiles back, that sweet smile of his that seems to spread across every inch of his skin. "He is persistent, isn't he?" he says.

"Like gravity. Or erosion."

They kiss, small, awkward kisses with lips still curled into smiles. John pulls away, thumb stroking her cheek. "I love you, you know."

Her stomach still flips when he says it, and she kisses him again, whispering her response against his lips.

The fatigue of the day catches up with her, and she pulls back before she yawns into John's mouth.

John smiles at her, but it's obvious he won't be awake long either, his eyes already at half mast. "So, do we just... invite him in? Seduce him? Tackle him on the sofa before we drag him upstairs?"

"We've got a fair bit to work out before we get to that point, I think," she says as she reaches down to pull the sheets over them, deciding to ignore the fact that they're still clothed. "But I'm sure we'll think of something."

"You do know that whatever we decide to do, he'll figure it out and run rings around us."

"Of course," she agrees as she curls into John before closing her eyes and drifting off.

* * *

Sarah slips out of bed around two and pads downstairs to grab a glass of water from the kitchen.

She meanders into the living room where Sherlock is somehow taking up the entire sofa, even though he's only physically occupying one of the cushions. The detritus of genius is scattered about him. Folders and notes litter one cushion. A half-dozen mugs and water glasses are within an arm's radius of him, each with varying levels of fluids left inside them. The blanket John stubbornly insists belongs on the _back_ of the sofa when not in use is lumped in one corner. There's a half-eaten sandwich on a plate in front of it, and Sarah is amused to see that it looks as though the blanket had been peckish.

The armchairs are heaped with more folders, newspaper clippings, and crime journals.

Sherlock never once looks up or greets her, but he's no doubt aware of her presence.

"Budge up, Sherlock."

He doesn't look up from the notes he's scanning. "Tea?" he asks by way of negotiation.

Sarah sets her glass on the end table, retrieving the plate, mugs, and water glasses. She turns the kettle on and fills the sink with soapy water. Her nice, modern flat has a dishwasher, so doing the washing up here is somewhat of a novelty. It reminds her of growing up, dinners with her parents. Well, it usually does, until she finds a body part in one of the coffee mugs.

Her nice, modern flat is immaculate. And empty. And as much as the clutter and chaos of 221B might get to her on occasion, she cannot imagine that she'll want to spend many nights alone when both John and Sherlock are here. And it's simply impossible to imagine John and Sherlock trekking across London together to spend the night at her place.

 _Is there even room for me here?_ she wonders and makes a mental note to talk to John about her future living arrangements. She grips the worktop as she tries to decide whether this mental note is more or less terrifying than the ones that read 'Research successful threesome relationships' and 'Figure out how to seduce boyfriend's genius flatmate.'

The kettle flicks off, and she sets the tea to brewing before she returns to the sink. She flips a mug over as she washes it, smiling. By all rights she should feel horribly self-conscious about being alone with Sherlock. She probably still smells of sex and sweat, and he'd been watching her. Watching her and John.

But she feels as comfortable with him as ever. Well, as comfortable as she's been since she survived his initial dissection. Perhaps she toughened up during those first couple of months when Sherlock scrutinised her so thoroughly that it seemed as if he could see through her clothes, through her skin.

Those months when he always looked surprised when something vapid _didn't_ come out of her mouth. And when that happened with enough frequency she slowly got upgraded from 'might be acceptable for John to date' to 'isn't onerous to be around' to 'may occasionally say something insightful'.

Sarah carries two mugs into the living room, grinning at the sight. The blanket is stretched out on the back of the sofa. The plate has been moved to the coffee table and now contains only crusts.

She passes Sherlock his tea before she settles onto the cushion he's cleared for her. He says, "Thank you," as he usually does when Sarah does things for him, which alternately satisfies John that Sherlock doesn't consider her yet another of Sherlock's many footmen and drives him mad that he doesn't afford John the same courtesy.

She drinks her tea while Sherlock continues reviewing whatever files he's examining. He's engrossed in them, focused, and she feels absurdly proud that he set them aside earlier to watch upstairs.

Cold cases. They must be. Sherlock isn't emitting that manic energy that hovers around him during active ones. She squints at the paper nearest to her, and it takes her sleep-addled brain a moment to realise the notes are in French.

This must be a new development. John hasn't told her about it yet, and he would be impressed by this, would be certain to rave about the latest spectacular discovery he's made into his study of Sherlock Holmes. Though as much as she teases John about his crush on Sherlock, the one that they both know is really far more than a crush, she enjoys hearing John's anecdotes as much as he enjoys telling them. She takes a sip of tea to hide the enormous grin that Sherlock _will_ ask about if he sees it.

He is acutely aware at the most inconvenient of times, and yet oblivious at others. From any other person, this standing in the hallway business would be disturbing. But it is so very like Sherlock for him to be insatiably curious and yet paralysed and tentative and cautious, waiting for them to invite him before he takes the last step. She'd never have thought him cautious when she first met him, but that was before she'd seen him dance around his affection for John for months.

Sherlock is still flicking through papers when she sets her mug on the end table and closes her eyes for a moment, imagining Sherlock putting the papers aside and curling up next to her. Not that he would. Not now. Not when he's not absolutely certain that it would be welcome. And certainly not without John here.

Sherlock is affectionate when he thinks the moment will conceal it. Oh, he's got no concept of personal space, that's true enough, but Sarah suspects that's more about testing what he can get away with than it is about touching, about getting what he wants.

She's not a genius of deduction, but she knows a fair amount about reading body language, about the way a patient's body tells you what questions they don't want to ask and what details they'd rather not admit out loud.

So she can read the nervous flickers of Sherlock's eyes, can interpret the small liberties he takes when he thinks the situation allows for it. He _craves_ physical affection – craves the connection, really – but is very, very aware that there are social norms about what is and isn't acceptable. Social norms that he has no clue how to navigate.

So he crafted his persona, his neatly constructed public persona that holds people at arm's length, mutters _offensive_ , caustic remarks to keep anyone who might have power or influence over him from getting too close (yes, she's noticed he treats Angelo and Mrs Hudson markedly differently from anyone at the Yard), and cultivates his sociopath persona, disguising and layering with motives that he'll rattle off a little too quickly for them not to have been rehearsed. And he's like that, in public when she sees him at the surgery or when he barges into a restaurant to whisk John away.

But that public persona is not congruent with the easy way he usually gets along with John, the way his posture shifts, instantly relaxing, when he arrives home, or the way he has begun touching both John and Sarah more often, increasing the geography of what he'll touch as though he's exploring it, charting out what's allowed, firmly establishing that it's safe before he expands his territory again.

All of the subtlety of Sherlock's exploration is completely lost on John, who is unbelievably compartmentalised in his ability to notice details. He can read physical symptoms, but body language (save for flirting) might as well be particle physics. And he is wholly unable to weigh Sherlock's actions against the motivations behind them or figure out what his motivations really are.

She'd nearly strangled John last month when he teased Sherlock for helping Sarah into her coat. Sherlock had frozen, her coat suspended mid-air. "Shush, John," she'd said as she slipped into the coat and leaned into Sherlock's touch. "You don't have a monopoly on treating me nicely, you know." She might have imagined it, but she swears Sherlock squeezed her shoulders before letting go.

That began an almost comical battle of chivalry, John constantly trying to outdo Sherlock, and Sherlock taking every advantage to take her arm, her hand, press his hand against her back as he guided her through a door. Though she didn't complain, even if she did leave the surgery for lunch more frequently, just for the novelty of opening a door for herself. And it was a far sight better than John's usual passive-aggressive battles with his flatmate. Just mentioning the word 'toes' sets John off on a twenty-minute tirade about how Sherlock purposefully annoys him.

And those battles absolutely must stop if the three of them are going to be together. She bites back an exhausted sigh as she adds 'Lecture John on not picking fights with his skittish flatmate' to her growing mental list of things to be resolved before they embark on this. Not that Sherlock helps matters. Hopefully it's all just pent-up sexual tension, and Sherlock doesn't just enjoy frustrating John... like the time he only spoke German, which drove John batty for two days until he downloaded a translation app for his mobile.

Sarah starts, her eyes flying open, when Sherlock dives for his mobile, firing off three different texts before he leans back against the sofa, a smile slowly creeping into his expression. He looks satisfied, as satiated as most people would after a rich meal, which, given the man in question, is probably a fitting equivalent. He grabs his tea off the table, seemingly uncaring that it's surely gone cold by now.

He sips the tea for a moment before he gathers the ring of papers around him and tucks them into a folder. He checks the time on his mobile, smirking, then exchanges one folder for another, spreading a new batch of crime scene photos on the coffee table, immediately immersed in them. Sarah averts her eyes. Since she began dating John, she's grown accustomed to crime scenes, even tagged along once or twice, but even still, gruesome murder photos before bed still guarantee nightmares.

She closes her eyes again, trying to remember what she was thinking about. Ah, Sherlock and his ridiculous persona, the one that he likes to think shields him against the rest of the world and their opinions. The one that apparently works for everyone but her and possibly Mycroft; she never can quite tell whether Mycroft is seeing _through_ Sherlock's façade or simply pretending that he can.

They'll have to find a way to slip past his persona, his defences. Because as much as he trusts John, he won't trust _this_. Her mental list of discussions to have, decisions to be made, is growing obscenely long.

She cracks open her eyes to watch Sherlock again, now flipping through case notes and cursing softly in French, of course. He is majestic while he works, swept into the world where he feels most comfortable, where his talents are treasured, even if not openly appreciated. _This_ is Sherlock Holmes, and he will be worth all the trouble of navigating around his peculiarities.

She really ought to crawl back into bed with John, but the sofa is comfortable, and Sherlock's quiet murmuring is tranquillising. She knows she's going to nod off, and the bed is simply too far away, up too many stairs. So she curls up at her end of the sofa, pillowing her head on her arm.

When she wakes up in the morning, still tucked in the same position, the blanket is wrapped around her.

**Notes for the Chapter:**

> Thanks to alpha, beta, and Britpicking Team of Dreams: christev, sc010f, machshefa, annietalbot, and cyanide_faery for beating this story into shape and encouraging it to grow far, far, far beyond its original scope.


	2. D (Delta) "Keep clear of me; I am manoeuvring with difficulty."

The first time had been an accident. Sherlock had arrived home late one night, his trip to Bart's taking longer than expected. He hadn't known Sarah was over, honestly. But it had been obvious that John was home; whatever he had been doing upstairs had been causing quite a racket.

Sherlock had gone upstairs to ask John about... something. His mind had been diverted elsewhere, likely still on his research, and he stupidly took the moans he heard on the stairs as an indication John was having another nightmare. It wasn't until Sherlock had his hand on the doorknob, the door half open, that he registered _two_ sets of moans.

He had been mesmerised by the sight. Sarah, with her back to the door, had been sitting atop John, alternating between rocking and grinding against him. She was exquisite, but it was the look of wonder in John's eyes that had stolen Sherlock's breath.

He'd seen that look on John's face before, yes, usually at crime scenes when Sherlock made a deduction that left John fumbling with words like 'brilliant' and 'amazing'. But never had it appeared for something so mundane as _sex_. And John was, despite initial, outward appearances, not a simple man, prone to excitement over fleeting trivialities.

Sherlock had concluded that perhaps he had missed a very critical element of the sexual experience.

And so he'd taken up the habit of observing John and Sarah.

Each time he watches, they go upstairs, and he waits ten to fifteen minutes for them to get past their tedious kissing and disrobing rituals – one viewing of that portion of the mating dance had been dull enough. Though if they're particularly eager, he can shorten the waiting period to as little as five minutes.

Once Sherlock determines the coast is clear, he follows, waiting, if necessary, in the hallway with his ear to the door until their moans began in earnest, the snippets of conversation taper off, and the bedsprings pick up tempo (usually a steady 4/4 time, though if John's feeling especially energetic, he'll slip into 6/8).

Then he turns the now-well-oiled door handle and watches.

Despite how engrossed the participants normally are in the proceedings, Sherlock had known it was simply a matter of time before John noticed. He isn't _that_ unobservant, not any longer.

Sherlock had noticed, of course, the moment that John had discovered Sherlock's surveillance, and he'd braced for the inevitable boring accusations about invasion of privacy. But the confrontation never came. John never raised the issue, changed nothing substantial in his daytime interactions with Sherlock, though he began watching Sherlock when he thought he could get away with it.

But John's interactions with Sarah changed. John began performing like a bloody circus seal, seemingly intent to prove that he and Sarah could contort into an endless array of sexual positions.

Apparently, John is an exhibitionist.

But, no, that hadn't been what initially put the look of awe on John's face. John hadn't known then that Sherlock was watching. It's something else. Something that eludes Sherlock. He _still_ hasn't been able to isolate the variable that causes it, despite a number of discarded theories.

It can't be attributed to Sarah clenching her pelvic floor muscles – John has a particular groan that accompanies that manoeuvre. It doesn't seem to be tied to position – John has a fortuitous natural tendency towards repeatability of conditions. And it isn't linked to Sarah ovulating, although the duration of their encounters nearly doubles during that week of her cycle.

It's something else, and it gnaws and claws at Sherlock, this hidden variable that hasn't yet surfaced to explain John's unpredictable expression.

So he keeps watching them, observing.

And so it is that Sherlock finds himself lurking in the hallway outside John's room, watching yet another encounter between John and Sarah. John has found a new position, just when he'd begun to repeat positions with increasing regularity, so much so that Sherlock had concluded John had reached the boundaries of his sexual knowledge.

They are situated such that Sherlock can view both of them from the side, John sitting cross-legged with Sarah in his lap, one hand trailing up and down her back while the other tangles in her hair. Sarah's arms are wrapped around John, clutching at his shoulders from behind. At first glance, Sherlock thinks he's miscalculated and arrived before the requisite kissing and fondling session has come to a close. But then he notices Sarah's hips moving, albeit slowly and with a small range of motion.

Sherlock cannot determine what is so satisfying about the position. It affords them little friction or freedom of movement, and it can't be comfortable for John to be bearing the bulk of Sarah's weight. But they are moaning as though they've just invented sexual intercourse.

Their lips disengage, and they rest their foreheads together for a moment before pulling back to look at one another.

The awe – and Sherlock is sure that word is wholly inadequate – in both their expressions nearly sends Sherlock staggering.

Sherlock has seen lust. He's seen passion. He's seen devotion and betrayal. Those are the things that spark violent, passionate crimes, after all. Of course he's seen them, or at least the wake they leave behind.

And belatedly, stupidly, like the idiots he rails against daily, hourly, he gets it. He hasn't seen _love_.

Certainly not true in the more common, more casual cases, but here, between John and Sarah, the sex is about connection, about peeling back the layers that separate them, about stripping away whatever gets in between them during their daily lives and forging, strengthening this nearly tangible bond between them. It's as close as they can come to crawling inside each others' skin.

It twists something in his gut to see them now, and he can't get down the stairs fast enough, barely remembering to shut the door before he goes.

He sits in the living room in the dark for a long time, thinking about how he will never experience what he's seen upstairs. And for the first time, Sherlock thinks he might hate being a sociopath.

* * *

Sherlock has stopped watching them.

Because he's completed his Survey into the Sexual Habits of John Watson and Sarah Sawyer. He's solved the puzzle, deduced the answers he was looking for. Watching any more would be pointless. He's certainly seen all the permutations already.

Sherlock spends a good deal of time actively ignoring them instead. He's self-aware enough to know that it is out of character for him to be treating a problem in this manner, but there's nothing else to be done. He's sure this is one of the issues classified as interpersonal relations, and since he knows fuck-all about solving _those_ kinds of problems, he simply spends as much time as possible away from the flat.

John has noticed, of course. It would be difficult for him not to when Sherlock bolts from the flat at the mere mention of the word 'Sarah'. Sherlock hasn't seen her, hasn't seen them together, since he stopped watching them, so he doesn't know for certain what it will feel like to see them, to risk seeing that look. But he's not inclined to find out.

Instead, Sherlock has accomplished a remarkable amount of work in the past two weeks, despite radio silence from Scotland Yard. He's submitted four articles to the British Journal of Forensic Practice. Not something he'd usually waste time with, but Sherlock has decided that he refuses to leave John's idiotic blog entries as his only legacy.

He's even bargained for some dedicated research space at Bart's, which has helped magnificently in keeping him away from Baker Street. And the ability to conduct multiple experiments in one room without having to accommodate anyone's concerns about food safety more than makes up for the inconvenience of travelling back and forth between the flat and Bart's.

Sherlock's sitting cross-legged on the sofa, beginning to type out his notes for his next article on countering the effects of embalming agents on soft tissue analysis, when John walks into the living room, fiddling with the cuffs of his suit, the one he normally reserves for weddings and funerals.

"So, uh, Sarah and I are going out in a bit. I need to pick her up in, oh goodness, twenty minutes. Have you got anything on tonight, Sherlock?" John asks, voice cautious and tentative.

"No," Sherlock replies curtly, eyes riveted to the screen.

"Sarah won a night at one of the fancy hotels in Kensington. Royal Garden, I think. So, that's where we're headed after dinner."

"How very lovely for you," Sherlock says. "Are you having trouble performing now that you don't have an audience? Perhaps you can pay the porter twenty quid and he'll sit in on of those nasty hotel armchairs and watch."

The room is silent.

He continues, "Oh, and do remember to remove the duvet on the bed. Nasty little petri dishes of other people's ejaculate."

In the reflection of the screen, Sherlock can see John gaping at him, staring with a look of hurt as though he's just run into an invisible door.

"Go. You'll be late to pick up _Sarah_."

The door slams shut, and Sherlock stares at the wall for a moment, thinking that perhaps his outburst had revealed a bit more than he intended.

Silence thunders through the flat as the echo of the slamming door and John's footsteps pounding down the stairs reverberates inside Sherlock's head.

Yes, he definitely hates being a sociopath.

**Notes for the Chapter:**

> Thanks to alpha, beta, and Britpicking Team of Dreams: christev, sc010f, machshefa, annietalbot, and cyanide_faery for beating this story into shape and encouraging it to grow far, far, far beyond its original scope.


	3. U (Uniform) "You are running into danger"

John has worried his meticulously crafted appearance into total disarray by the time he arrives at Sarah's.

Sarah is smiling, beaming and gorgeous, when she opens the door, and it all slides off her face immediately once she takes in his expression. "What is it, John?" she asks.

He blurts out, "I was right. There is something wrong. Something very, very wrong with Sherlock."

She freezes as she's reaching for her handbag. "Should I call the restaurant, then?"

"No, no, nothing like that. He's just being an arse. We should go eat. Oh, God, _I'm_ an arse. You look lovely," he says, leaning in to kiss her. "More than lovely. You're beautiful."

She smiles into his kisses. "We'll get things sorted. We do need to go though," she says, nudging him out the door and locking it behind them.

They've got reservations at this new bistro around the corner from her flat, and John has never wanted to eat less in his life, despite the way his stomach is growling.

They're seated, meals ordered, wine glasses in hand when Sarah asks, "What's Sherlock gone and done, then?"

John tells her about what happened at the flat and watches her jaw drop when he gets to the part about the porter, which of course happens just as the waiter arrives to deliver their starters.

Once they've got over their embarrassment and subsequent laughter – which really, truly goes a long way towards unravelling the knot in John's stomach; he _loves_ this woman – Sarah asks, "So, what's got wrong with Sherlock?"

"I have no idea! It could be anything."

Their food arrives, and John begins moving the pasta around on his plate. "And he's never home any more. He's always off at Bart's or consulting on some white collar crime that he says he doesn't need my assistance with. It's as if he's gone and..."

John winces.

"What?"

"It's as if he's married to his work," he admits, shoulders sinking.

Sarah flinches, having heard him quote _that_ conversation all too often enough recent weeks. She chews a bite of whatever unpronounceable main course she'd ordered. "Well, have you talked to him about it?"

"What? No, of course I haven't talked to him about it."

Sarah rolls her eyes at him before taking another bite, mulling things over as she chews. "Do you think he's feeling left out? Maybe we should have invited him to join us a week or two ago..."

"If he was feeling left out, it'd be just like it was when we were first dating. You know, popping in on every date, interrupting our phone calls, texting me during the middle of sex, generally clinging to me like he was afraid I was going to evaporate."

She considers this and nods. "Look, I know the plan was to go to the hotel and text him, but you've hardly touched your food, and I'm full enough already. Why don't we get the rest wrapped up, and go back to your flat?"

John agrees, and before long, they're in a taxi back to Baker Street. John is _not sure_ he can confront Sherlock about this. If Sherlock is still in the mood from earlier, he will rip them to shreds.

Sarah finally grabs both of his hands to stop them from shaking.

John continues holding Sarah's hand as they climb the stairs, and he thinks that whatever pasta he did actually eat was a horrible mistake because he can feel his stomach twisting around it.

They stop outside the door, and before John fumbles for his key, he kisses Sarah, a bit more desperately than he intended.

She chuckles against him. "This isn't the Inquisition, you know. Everything will be fine."

John bypasses the obvious joke – he is too unnerved: he'll start giggling and won't be able to stop.

Sherlock scowls at them when they walk into the living room. He hasn't budged from where he was earlier. "Well, you both are back considerably earlier than advertised," he says, snapping his laptop shut and beginning to collect his papers.

"You don't have to run off just because we've returned," John retorts, already pissed off at Sherlock's behaviour.

Sherlock's eyes narrow and he directs his attention to Sarah. "You're wearing red and showing considerably more skin than you normally do, even when you're ovulating, which you won't do for another week. John was rather a sure thing this evening. Why did you tart yourself up tonight, Sarah?"

A scathing defence is on the tip of John's tongue, but Sarah pre-empts him. His beautiful, strong, brave Sarah smiles in the face of Sherlock's barb and simply sits next to him on the sofa, toeing off her heels and tucking her feet beside her.

John has to cover his mouth with his hand to hide his smile. Sherlock's eyes have grown wide, and John can _see_ him trying to figure out what Sarah is doing.

She smiles up at John, eyes sparkling. "Would you put our food in the fridge, John?"

John deposits the takeaway containers in the fridge, staring at its insides for a long moment. It's held no experiments, no body parts since Sherlock's started haring off to Bart's. It really, really shouldn't make John's heart twist because the kitchen is, for once, food-safe. He's only been nagging Sherlock about since they moved in together.

Frowning, he returns to the living room, propping himself against the doorway. Sarah seems willing to take the reins on this, and she can have them.

He watches, arms crossed, as Sarah somehow manages to make this conversation happen without treating Sherlock like a five-year-old whose parents have been called home early from their evening out. She is brilliant.

"Sherlock, do you know why we came back to the flat tonight?" she says, her voice even and gentle.

Sherlock rolls his eyes. "There are any number of reasonable, mundane explanations. It's possible John left something here. Or you were mistaken about the hotel reservation."

Sherlock is winding up to list _all_ of the possible explanations when Sarah cuts him off. "We came back because we were concerned about how you reacted to John earlier. We _had planned_ on inviting you to the hotel after dinner, Sherlock, to join us... to be with us."

Sherlock gapes at her, shocked, as if she's actually reached in and stolen words from his mouth and he can't figure out how to get them back. He's speechless and staring for what seems like minutes before his eyes narrow and he responds stiffly, "I think you misinterpreted my presence outside John's bedroom."

John wonders if Sherlock realises how pathetic a comeback this is.

"I don't think we misinterpreted it at all. I'm sure you're going to tell me it was some sort of data gathering mission," Sarah says, the corners of her mouth twitching when Sherlock's stirrings of protest are cut off.

"But I know it's more than that. You left behind _four boxes_ of case files in the living room to watch us one night. You chose something as 'boring and pedestrian' as sexual intercourse because there was something about what we were doing that was more captivating than crime scenes, Sherlock. And whatever it was you saw, whatever attracted you, we want to share that with you."

John is holding his breath. He can't help but think that Sarah's gone completely out on a limb, and he hopes, desperately hopes, that her guess is correct. Because if Sherlock hurts her right now, their friendship will not survive this.

"You have both lost your minds. I do not..." Sherlock grumbles, trailing off as he sets his stack of papers onto the coffee table. "John, you're not even interested in men, and you seem to keep Sarah quite well satisfied. Her physiological responses indicate that she's not faking her orgasms. Given the frequency with which you two shag one another, your sex lives cannot _possibly_ be lacking. I don't need some sort of pity shag just because you two have decided my libido needs tending."

"First off, wrong about the interest in men. Second, that's not what we're after," John interjects, watching as his revelation forces Sherlock to reconfigure the evidence he has stored away inside his head. He hadn't believed Sarah when she'd lectured him about it, but John can see it now. It is crystal clear the way Sherlock uses evidence, uses deductions as a protective barrier.

After a moment, Sherlock asks, his voice flat, revealing absolutely nothing of his own opinion on the matter, "And what is it that you're after?"

Every muscle of Sherlock's body language yells at John not to crowd him, not to push him. Sarah, obviously, picked up on it first. She's close to him, yes, but she hasn't touched him.

So as much as John wants to sit on the sofa with them, wants to tangle himself in their arms, their legs, their hair, he lowers himself into his armchair and exhales. "We all get along quite well. Sarah and I both find you very attractive. That attraction appears to be mutual, and it's normal in such situations to... act on that."

"I cannot believe you're advocating this, John. You tell me _daily_ how you wish I behaved differently, enumerating all the little ways I annoy you."

John bites back a sigh. Of course Sherlock is fighting him on this. He won't believe them until he's picked up the evidence and examined it from fifteen different directions, trying to make it disintegrate.

"Because you are maddening, Sherlock. And yet I'm still here. Look, this isn't a mystery or logic puzzle to be solved. You just... you fit with us, Sherlock."

Sherlock cringes, and John's not sure whether it's the black hole of logic in John's argument or whether John and Sarah really did read the situation incorrectly, projecting their own desires onto Sherlock.

"I don't _fit_ with anyone, John. And there is no reason to expect that bringing me into your bedroom... well, no, it would have to be mine. Yours is too small."

John grins. If Sherlock is making the leap to logistics, then he's not going to reject their invitation. He moves from the armchair to sit next to Sherlock.

Sherlock fidgets between them, staring at the discarded stack of papers.

"Sherlock, look at me," John says, sliding his arm onto the back of the sofa.

After minutes, hours, Sherlock's eyes meet his. "You can say no. You can push us away, and we'll try to go back to normal. But please give us a chance," John says, chucking any bit of reserve to the wind and flat out begging.

At great length, Sherlock nods, his neck as stiff as if dipping his head is as difficult as pushing a lorry up a hill.

John grins so widely that the smile radiates heat. His face feels flushed as his – yes, now he can admit it – love and affection for Sherlock washes away the dread and fear of the past week. John breaks eye contact to look at Sarah and sees his smile mirrored on her face.

He shifts closer to Sherlock on the sofa, and his breath catches when he looks at Sherlock again. He seems mesmerised, entranced. Then Sherlock's gaze flickers to Sarah and back, and John can see Sherlock's mind tumbling as if his world view has been blown apart and he's trying to glue all the little bits back together so he can deduce what it means.

Sherlock's bewildered expression stabs through John. He's only looked at John like this once before, and at the time John had been covered in Semtex, stepping out to confront his flatmate, his partner in crime-fighting, his now-soon-to-be lover.

But then Sherlock relaxes, his expression losing that mentally strained look, and John's close enough to him that he can feel the ragged breath that Sherlock exhales. Relief is replaced by acceptance and quickly exchanged for something John cannot quantify. Joy? Hope? Happiness?

And then Sherlock's hand is on John's hip, and he's not sure who pulls whom, but John is flush against Sherlock's side, straddling his leg, as he tangles his left hand in Sherlock's hair and Sherlock's lips spark against his.

He tilts his head and runs his tongue along Sherlock's lower lip, once, twice, and then Sherlock's mouth is open and his tongue's brushing against John's. Sherlock's hand leaves his hip and winds its way beneath John's suit jacket, the heat and pressure of his fingers against the small of John's back leaving him gasping and moaning into Sherlock's mouth. This _must_ work out, it has to, because he _needs_ this, needs Sherlock.

John pulls away, panting, and looks at Sarah. He's sure his expression is utterly moronic, and he just barely stops himself from blurting out, "You _have_ to try that, Sarah."

Sarah doesn't need words, hardly needs suggestion. She twists so that she's half-kneeling, half-sitting with her left leg planted between Sherlock's legs, nestled firmly against John's right, and she kisses Sherlock, skipping over chaste and slipping her tongue immediately in between his parted, panting lips.

John could watch them kiss all night, could watch their lips and tongues forever.

And then Sherlock's left hand trails down Sarah's back, lower, lower, lower, until John sees those long, delicate fingers wrap around the inside of Sarah's thigh underneath her skirt.

Those fingers. He wants to see those fingers inside Sarah, wringing out her last orgasm of the night after they've shagged themselves silly. He wants to see those fingers tugging at his cock, wrapping around it. He wants to see those fingers wrapped around _both_ their cocks.

John lets out a strangled moan.

Sherlock pulls back from kissing Sarah, eyes unfocused. "I think..." he pauses, trying to catch his breath, "you mentioned a hotel earlier, John?"

"Oh, thank God."

It takes them ages to get their coats on, between the kissing and groping and Sherlock pressing Sarah against the wall and damn near shagging her right there in the hallway. The coats are not strictly necessary given the weather, but John is not keen to advertise their situation to Greater London. And Little John is advertising.

John wonders how they're going to survive the cab ride without getting tossed out on the kerb by the cabbie.

There's an awkward bit of jostling and figuring out who's going to sit in the middle when they get in the cab, but it passes without fanfare, and Sarah's nestled between him and Sherlock. And when Sarah slips her hand into Sherlock's, John _knows_ he's grinning like an idiot.

This is brilliant. Not even the sex. The sex they're going to have. Haven't had. Almost didn't have. Anyway, if there was any doubt that _this_ , sharing all this with Sherlock, was the right decision, it's gone. It vanishes the moment Sherlock turns to look out the window and John sees his horribly concealed smile in the reflection.

John keeps his distance, doesn't touch Sarah, because that tiny bit of space is all that's keeping his self-control in check. So he watches them, watches Sarah's shining face, watches Sherlock's thumb tracing across her hand until even that is too much.

So he stares out the window of the cab, and, thank God, they're finally here.

**Notes for the Chapter:**

> A million billion thank yous to the alpha/beta/Britpicking armada who've helped launch this story: Annietalbot, Christev, cyanide_faery, machshefa, and Sc010f. *continues to abuse naval metaphors*


	4. X (Xray) "Stop carrying out your intentions and watch for my signals."

As he exits the cab, it hits John that he and Sarah have thoroughly, very thoroughly, discussed whether they wanted to make this decision and what its implications would be on their relationship. And they have discussed the strategy for getting Sherlock to the hotel many, many times; John has had a text sitting in his draft folder for a week. 'Royal Garden Hotel, Kensington. Require your assistance. Could be dangerous.' God, he'd thought himself so clever.

But they have never successfully discussed _how_ things will play out in bed. They'd tried. Countless, innumerable times, they'd tried. But they'd always ended up rather distracted.

John nearly freezes in the entryway to the hotel with the terrifying thought that they've never talked about who will be in the middle. Or if there won't be a middle, if they'll just take turns pairing off while the other watches or...

Sarah places a hand on the small of his back and pushes him through the doorway. She leaves them to wander around the lobby, John trying to affect an air of nonchalance.

The wait while Sarah checks in is interminable, not in the least because _Sherlock_ is interminable. He picks apart the lobby, deducing everything and everyone in it until John is so desperate for a moment of quiet that he considers kissing Sherlock for the sake of shutting him up. But a glance at Sherlock makes John suspect this was his intent all along.

And then Sherlock's expression softens, the mask he adopts for crime scene deduction drops, and John realizes that the entire journey into the lurid past-lives of the hotel lobby has been a distraction. A simple distraction.

John stares at Sherlock, blinking, and wonders how his normally socially clueless flatmate managed to infer the proper course of action to keep John from getting nervous. And then John looks, really looks, at Sherlock. No, this wasn't about John's nerves at all. It was about Sherlock's. The great Sherlock Holmes is nervous. John's heart pitches.

Sarah walks up with the room key before John can say a word.

The lift takes ages to arrive. They say nothing to one another while they're standing, waiting for it. There's nothing _to_ say. There's not a single bit of small talk that's appropriate. John spends the time glancing around them, certain that everyone is watching them, that the entire hotel knows what they're about to do.

Sherlock leans over and whispers, "No one knows, John. Well, I suspect the receptionist has an idea, but he's just jealous."

John bites back a whimper as Sherlock's breath tickles his ear.

Finally, finally the lift arrives, and they hurry inside. Sarah mashes the button for the 9th floor with one hand while the other presses the button to close the lift doors. John is coiled, ready to pounce the moment the doors shut, but his movement is arrested by Sherlock's voice.

"I didn't realize your exhibitionist streak extended _this_ far, John."

"What?" John says, voice clipped.

"Cameras, John. Though by all means, go ahead if that's your thing. I'm sure whoever is watching will appreciate the show," Sherlock drawls, pronouncing the word 'whoever' in that same tone he uses to say 'Mycroft', and John swears his erection crawls back inside his body.

Sarah shakes her head, grinning, before she admonishes Sherlock, "Stop teasing."

The look Sherlock gives her is petulant, but it immediately morphs into this... magnetic thing that has John certain that Sarah and Sherlock are, in fact, going to shag in the elevator in approximately ten seconds, cameras be damned.

Then the lift doors open, and Sarah's charging down the hall, brandishing the key like she's leading a battle charge.

John and Sherlock follow as briskly as their uncomfortably tight trousers allow.

Sarah has the door open and is flicking on lights when they arrive. The door bangs shut behind them, and they press Sarah against the wall, legs, arms, mouths, throats tangled together.

John kisses Sarah's mouth as Sherlock sucks at her throat, and she is moaning, her hands wrapped around their heads. John's hands are everywhere, one moment stroking Sarah's breast, her thigh, then Sherlock's arse.

Sherlock's breath is short and ragged, and when John's hand presses against his prick, he moans John's name into Sarah's neck.

Sarah shivers then pushes at them. "Bed," she demands.

John tugs her towards the bed, pulling her on top of him and pressing a row of open-mouthed kisses along her neck. It takes him a moment to register that Sherlock hasn't joined them.

Eyes hazy with lust, John breaks off kissing Sarah to look at Sherlock, who is standing by the wall looking disgusted.

"Wha?" John slurs.

"The duvet, John. I refuse to join you on the bed until you've moved the duvet."

John shakes his head, grinning, but nudges Sarah off him, and they stand, moving to opposite sides of the enormous bed. He picks up a corner, touching the least amount of duvet possible. He already wants to wash his hands, and he suspects Sherlock will have ruined him for hotels forever. Sarah picks up the other side, and together they fold the offending bit of fabric.

Sherlock sits at the centre of the foot of the bed and surveys the bed's parameters, holding his arm out to assess its fit. Then, his feet planted on the floor and hands gripping the edge of the mattress, he tests the bed's bounce.

John grins, amused that even here Sherlock cannot resist his inherent compulsion to investigate, to experiment, to test. John shudders as he thinks how that compulsion will be methodically directed towards him and Sarah.

Although at the moment, they risk losing Sherlock to mattress inspection.

Sarah has placed the duvet on the dresser, and John catches her wrist, guiding her in front of him so that they're both standing in front of Sherlock.

"Sherlock... watch," John says before nuzzling Sarah's neck and slowly unbuttoning her blouse.

The mattress is forgotten.

Sherlock's gaze is trained on Sarah now. Her moan vibrates against John's lips.

Her blouse falls to the floor, and John's breath catches. Her bra is sheer lace and pale pink, and John is sure he's never seen it before.

As his fingertips brush across the lace, he closes his eyes for a moment, enjoying the way her nipples harden at his touch.

"New?" Sherlock asks, though everyone in the room knows that he already knows the answer.

"Yes," Sarah hisses as John pulls a nipple in between his fingers, the lace rubbing against her.

John opens his eyes to see Sherlock swallow with difficulty. He seems fascinated, transfixed by Sarah, and – John's eyes flicker lower – very interested. Their eyes meet for a moment before Sherlock's attention returns to Sarah, his eyes raking over her, almost possessively before returning to look at John.

Sarah is _theirs_ , the look says. To share. John and Sherlock are going to share Sarah.

And he and Sarah are going to share themselves with Sherlock. Share each other with him.

And together they'll share Sherlock.

For a half a heartbeat, John is dizzy with what it is they're doing. What it is they're starting.

And he really, really needs to get her damn skirt out of the way so they can actually start it.

He nibbles at her earlobe as he fiddles with the clasp above the zip on her skirt. It is imperative that he see the matching knickers _now_.

Sherlock interrupts, "John, stop that. Sarah doesn't like it. Do it to me instead."

John is lost. He releases Sarah's earlobe from between his lips and blinks at Sherlock. "Stop what?"

"That thing with her ear."

"Bossy, are we? And what do you mean she doesn't like it? She's never said anything to me. You don't like it?" he asks, hoping, however foolishly, that Sherlock is wrong.

She shakes her head, but he can feel her almost silent laughter.

"Oh," John says flatly. Dammit. He does the ear thing rather often, and now he feels a complete prat. "You really don't like it?"

Sherlock sighs. "The sound of breathing in her ear reminds her of obscene phone calls, and the sound of your licking at the shell of her ear reminds her of her mother's cat grooming itself."

"It does?" John says, grimacing at both images.

"She tolerates it because _you_ seem to enjoy doing it, but now that I'm here she needn't make the sacrifice," Sherlock answers, voice smug, seemingly pleased that he knows something about John's lover that John has been too unobservant to notice.

It plucks at something irrational inside John that they are all still clothed and Sherlock is already directing. Not that John really expected otherwise, in the long run anyway. But John had hoped to maintain some measure of influence on the first round at the bare minimum.

John stalks to the bed and pushes Sherlock's shoulder, sending him tumbling back onto the mattress. John climbs over him, pinning his arms. John can hear the zip of Sarah's skirt, and it's all he can do not to turn around to see those matching knickers.

Sherlock is holding his breath, tense with anticipation, as John kneels above him, head lowered and mouth perched over his ear.

John makes damn sure that Sherlock can hear his breath before he sucks Sherlock's earlobe between his lips.

Sherlock's exhales a guttural, strangled sound that wraps around John's cock. "Like that, do you?" John whispers.

Sherlock whimpers – _whimpers_. "Yes. Yes, John, it's even better than I might have imagined."

John closes his eyes and breathes, at once irritated and aroused beyond belief. Releasing Sherlock's arms, he props himself up so he can look Sherlock in the eyes. He reminds himself that he and Sarah talked about this, that bringing Sherlock into their relationship would probably involve showing him exactly how one behaves in a relationship. "Just ask, Sherlock. Don't... the bedroom isn't... don't manipulate me, us. Next time just ask."

Sherlock stares at him for a moment, his eyes narrowing as he processes what John has said, weighing it alongside all the other evidence. He nods.

The bed dips next to them as Sarah lies down, saying, "Are you two done, then? Figured all that manly business of who's going to be in charge and whatnot?"

They both turn to look, well, gape once they take in the sight of Sarah in her new, pale pink bra and knickers. John's mouth goes dry.

"Well?"

John is too busy staring at the knickers to cobble together a response. They sit low on her hips as if they're suspended there, ready to fall off at any second.

Sherlock clears his throat and answers, "Yes, I think we're done. Did you have a specific course of action in mind, Sarah?"

John blinks and looks at Sherlock, on guard for the politeness that Sherlock only ever uses to get something he wants. But his expression isn't quite perfect enough for that. His eyes are glazed, and John's certain not even Sherlock could fake the arousal he feels pressing into his hip.

Sarah continues, "You're both rather wound up, and I think we ought to get in a round of something simple and easy before we go for anything elaborate."

"Something easy?" John repeats. For once, Sherlock doesn't chide him for the repetition. Either he's just as stupid with lust, or he's giving politeness in the bedroom a serious go.

"Why don't we get Sherlock's clothes off, John? Yours too."

John scurries from the bed and shucks all of his clothes in the time it takes Sarah to work Sherlock's shoes off his feet. She grins at him. "I'll just stick to the bottom half, then."

Sherlock is smiling, eyes half-closed, lids heavy, looking so dazed that John glances at his trousers to make sure he hasn't already come. No, he hasn't, not unless he has the refractory time of a sixteen-year-old.

He is watching John, eyes scraping over his body. If he didn't look so brain-addled, John would suspect that Sherlock was deducing his sexual history from his moles and freckles.

Sherlock is gorgeous, and John can't wait to see what he looks like when they're done with him. John lies next to him, careful to angle his body away from his flatmate's. Friction is _not_ something he needs at the moment, not if he wants to last until whatever Sarah has planned for him.

With one hand beginning to work at Sherlock's shirt, John kisses him, and it is nothing like their frenzied kiss earlier, a lifetime ago when they were back at the flat. No, these kisses are slow, almost lazy, their tongues dragging over one another, again and again.

John hears Sarah flick open Sherlock's belt buckle, feels his hips lift off the bed, and John hurries to undo the last of the shirt buttons, leaning away from Sherlock's heady kisses when the shirt's completely open.

Sherlock wriggles out of his shirt, looking about a hundred times more dignified than if John tried such a manoeuvre.

It's John's turn to observe now. To take in the ribs that aren't quite as visible as John had expected. The hip bones that jut out, as prominent as Sherlock's cheek bones. The full, thick cock that's so hard, looks as hard as John's cock, painfully hard.

John has to close his eyes when Sarah flicks her tongue across the tip of Sherlock's cock. It's too much. It's not even _his_ cock, and it's too much stimulation. From the sound of Sherlock's strangled moans, he feels the same way.

John has time to take two deep breaths before Sherlock pulls him back down into a demanding kiss. John reaches down to stroke Sherlock's nipple and feels his body contort at the touch. He sucks John's tongue, moaning around it, and it takes every last shred of John's willpower not to thrust his prick against his hand, against Sherlock, against the mattress, against the air.

He wants to see Sherlock's expression, how he looks at Sarah while her lips are wrapped around his cock. And he wants to see what it looks like when this beautiful, intense man falls apart, but Sherlock is clinging to him, kissing him as though John is vital to Sherlock's continued existence. And John is unable to deny him this. Will probably never be able to deny him anything again.

His fingers strum across Sherlock's nipple, plucking at it. And then Sherlock wrenches his hand away from John and curls it around Sarah's head. His body arches, and he comes, whimpering into John's kisses.

John stills his fingers, moving his hand to curve around Sherlock's stomach. He kisses him gently and then pulls away, grinning. John helped do this, helped undo Sherlock Holmes.

Sherlock's eyes are closed, and his chest is heaving as he attempts to catch his breath. His face is still flushed. His body glistens with sweat. He is even more stunning than normal. And his smile... John has no words to describe how utterly content and satisfied Sherlock looks.

John can practically feel the relief, the satisfaction rolling off Sherlock, and his own cock throbs jealously.

"That was... thank you, Sarah," Sherlock says, still panting.

Sarah crawls up the bed and curls up against Sherlock. "You're quite welcome," she murmurs before leaning in to kiss him, once, twice, before she looks up at John. "Well, your turn, love."

John hopes that he lasts more than a minute, but at this point, lasting thirty seconds once her lips wrap around him will count as victory. He is shaking when he lies down, and Sarah smiles at him, crawling over Sherlock to kiss John.

"Wait," Sherlock says, voice thick and groggy. "May I, John?"

The words scramble all the language centres in John's brain. Sherlock continues, "You did tell me to ask."

John swallows three times before he can respond. "Yes, fine. Go right ahead," he croaks.

Sherlock smiles and then prowls down the bed, settling between John's legs.

John wonders if he's going to live through having sex with Sherlock Holmes. He searches for a distraction, anything to keep him from coming the second Sherlock touches him. "You're awfully sure of yourself for someone who's only had sex a handful of times. How is that?"

"Paid attention to that, did you? Interesting. That conversation was... five months ago?"

John smiles. "Occasionally you do say something interesting. And you're avoiding my question."

The grin Sherlock gives him is feral. "I have data, John," he quips, biting the precise spot on John's hip that only Sarah has ever discovered. John's toes curl, and he digs his heels into the mattress.

And then Sarah, his – no, their – beautiful Sarah leans down and sucks on his earlobe just as Sherlock swallows him. John watches Sherlock's cheeks hollow once, twice, before he has to screw his eyes shut.

"Oh, oh my God, you, both of you. You feel so good," John babbles.

He clutches at the sheet, panting and trying not to think about Sherlock's fingers brushing the back of his knee or Sarah's fingers tugging at his nipple or Sherlock's tongue or Sarah's tongue or Sherlock's lips or Sarah's lips or...

John comes, arching, twisting, with all of his brain cells and neurons trying to escape his body through his prick.

When John has stopped orbiting, when his neurons and synapses agree to begin cooperating again, he opens his eyes. Sarah's still next to him, one arm wrapped around his waist and her fingers brushing along his ribs. Sherlock is behind Sarah, curled around her, hand stroking up and down her side, hip, and leg. They're both looking at him, watching him, and he offers them an assuredly dazed smile.

"Better now that we've taken the edge off a bit?" Sarah asks.

John grunts an affirmative. At length he expounds, "I think Sherlock sucked out my spinal cord."

Sherlock smiles, a quiet, hardly noticeable smile that John only ever sees when Sherlock gets complimented (usually by John) for something he's deemed especially worthy of praise. John adores that look and it thrills him to see it here, now.

"And you... when did you get these?" John asks, running a finger down Sarah's bra strap, over the lace, across her nipple.

Sherlock's hand deviates from its path along her side, and he runs one long finger under the elastic of Sarah's knickers.

"I spent the day doing a bit of shopping and pampering."

He slowly parses the sentence. John is not entirely certain – his brain's a bit muddy, after all – but he's fairly sure that translates to "I took myself shopping today for fancy new underthings to seduce you and your flatmate... and then I got so turned on I went home and took a very long bath and tried not to touch myself."

His prick seriously considers getting hard again.

Her breath hitches when Sherlock's fingers dip lower. John's vision has narrowed to those long fingers, hardly concealed by the lace, circling, stroking lower and lower.

"Today? Sounds like you could do with a bit of unwinding too," Sherlock says as his wrist joins his fingers beneath the waistband.

Even as she arches into his touch, Sarah shakes her head. "No, no unwinding necessary." She twists and kisses Sherlock as he continues stroking her.

God, they look magnificent together. Sherlock sucks Sarah's lower lip the way she likes it, and she moans. John feels his arousal returning, building inside his belly, licking at him. It ratchets higher when Sarah pulls away from Sherlock's lips to say, "I want you to fuck me, Sherlock."

John silently curses the knickers because he's certain Sherlock just answered Sarah's request by plunging two fingers inside her. He's about to shuffle towards Sarah so he can tug the knickers from her hips and get a better view when she says, "And I want John to fuck you."

John's heart stops. Not because the idea's exciting (it is, it really, really is), but because he's spent so long deliberately _not_ imagining this that he is suddenly overwhelmed. Without the haze of lust completely fogging his brain, it's a little too easy to think, to overthink.

Even in discussing this with Sarah, he has not allowed himself to actually visualize this, to think about his hands on Sherlock, _in_ Sherlock. He's limited himself to imagining Sherlock watching him and Sarah or thinking about Sarah and Sherlock together, in the abstract, under sheets with not a naughty body part in sight.

Because Sherlock would have known, long before John and Sarah were ready for Sherlock, before they'd talked through things and figured out what sharing their relationship with Sherlock would mean. Sherlock would have deduced it somehow – likely because John would have had to start icing his wrists on account of the dramatic uptick in wanking sessions.

And before... before Sherlock started watching them, John just couldn't let those thoughts bubble to the surface. Sherlock sent out so many mixed signals. No, not signals. Signals is too subtle a term. Sherlock's signals are about as subtle as foghorns. John thinks for a moment about whether there's a better word, but there really isn't. Foghorns it is.

So, yes, before Sherlock started watching them, he sent out so many conflicting foghorns that John had tamped down any flickers of interest before they could ignite into something more. John hadn't known, hadn't allowed himself to hope that Sherlock was actually interested in him.

Sherlock looks up at John, looks up from kissing Sarah, his eyes lust-filled and languorous, and John considers that the blow job Sherlock gave him earlier – and thank God he didn't think of the stupid foghorn metaphor before Sherlock blew him – might be a reasonable enough indicator that Sherlock is interested. And although the thought of shagging Sherlock is _actually_ terrifying, a little terror has never exactly stood in John's way before.

Sherlock crawls to John's side of the bed. He seems to briefly consider looming over John, perhaps pinning him to the bed like John had done earlier, but then he slots himself against John's side. Sherlock isn't exactly hesitant, but he seems a bit wary, cautious, like he too is aware they are about to officially step over that neat, precise line labelled 'flatmates'. Well, whatever parts of the line the blow job didn't obliterate.

They stare at one another a moment, and then Sherlock's lips quirk in that mischievous smile of his, and it's like that heartbeat before they dart off in pursuit of a suspect. That silent conversation where the words 'danger' and 'fun' hang, suspended in the air between them for a split-second before they launch themselves from standstill to sprint.

And then Sherlock's kissing him, hands frantic, tugging, touching, and roaming as if he's been holding back _months_ of pent-up energy and refuses to let go now that he can has free reign over John's body. For moments, John is caught up in the maelstrom that is Sherlock Holmes and his now unbridled affection. Sherlock's kisses are _electric_ , and dear God, Sherlock has wrapped his hand around both their pricks.

"Sherlock... _Sherlock_ , slow down," John says, his fingers stilling both of Sherlock's hands.

The look Sherlock gives him is so _needy_ that John stops breathing. And then John _remembers_ that random conversation from five months ago about Sherlock's sexual history and the implication that it may have been years, possibly a whole decade since Sherlock's had sex. Well, no wonder he's eager.

All the more reason John needs to slow things down a bit. He rolls Sherlock onto his back and kisses him slowly, his lips barely brushing once, twice, before he gently pulls Sherlock's lower lip between his. Sherlock moans into his mouth.

John's fingers are shaking... all of him is shaking as he reaches for Sarah's handbag on the bedside table, pulling out the lube and condoms and setting them on the table. He _needs_ Sherlock. Has needed him for a long time. He kisses Sherlock again then pulls away to open the lube. Sherlock grins _wickedly_ at the bottle.

It's no surprise whatsoever that Sherlock begins talking when John slips a finger inside him, then two. But where John might have expected streams of random facts, deductions, and instructions, Sherlock instead delivers a steady stream of vivid, pornographic feedback and encouragement.

Another finger and a string of "Yes, John, fucking _right there, now, harder, yes, there_ " convinces John that Sherlock is prepared enough. He slips his fingers out, trying not to grin when Sherlock glares at him.

"Sarah," John says, nodding towards her. She's stripped off her bra and knickers, and she is laying there, ready and waiting, her legs open. She is wet, so wet, and John has to bite back a whimper as he watches Sherlock settle in between Sarah's thighs, listens to her moan as he slides inside her.

They shift together, settling into a position that gives John room to kneel behind Sherlock. He sinks into Sherlock, slowly, so very slowly. It has been a _very_ long time since he's been inside another man, and he's forgotten how tight, how tense those first moments are. And Sherlock is tight... _so_ impossibly, unbelievably tight.

When he's all the way inside Sherlock, he takes a long moment to fully appreciate the fact that he is _inside_ Sherlock. His fingers trace along Sherlock's sides until they brush against Sarah's body. She places her hand on John's and squeezes.

Oh, fuck. This is perfect. He presses a kiss to Sherlock's spine, and he shivers underneath John, _around_ John.

He shifts his hips, trying to find a position where he can move and still touch everyone, but it becomes obvious in short order that physics are not on his side. He lets go of Sarah and grabs Sherlock's hips, relishing the way they feel under his fingers. Then he pulls back and thrusts and _everyone_ moans.

This is fantastic, Sherlock and Sarah underneath him. Although it seems that three people having sex make a lot of noise, and John soon gives up on being able to hear Sherlock or Sarah after twice asking Sherlock to repeat what he just mumbled. Sherlock's very clearly annunciated, 'I told Sarah I loved her tits' is... not so arousing.

So John closes his eyes and thinks about how he's really shagging both of them, how it's his thrusts that are driving Sherlock into Sarah. John focuses on the feel of Sherlock surrounding him, on the feel of Sherlock's hips underneath his fingers. And it's good, it really is.

But what he _wants_ to do is to talk to Sarah, to ask her filthy questions about how the experience is measuring up, but she is so bloody far away, miles away, on the other side of Sherlock. Sherlock's body apparently blocks sound as well as sight, so Sherlock would have to relay the damn messages. So if John says something, it won't be so much 'talking' as it will be 'corresponding.'

Sarah moans loudly, and John wonders what caused it, what felt that good. He realises he feels isolated back here, which is a completely ridiculous thing to think when your cock is buried inside someone.

Sherlock stops moving, his body rigid. The change is so abrupt that John stops moving, too. He spends a tense moment terrified that Sherlock is going to bolt out of the bed because he's forgotten an experiment or just figured out one of Lestrade's cold cases or, no, this just isn't working for him.

"John, come and lie down next to us," Sherlock says, patting the bed next to Sarah.

John's brow furrows. Not that Sherlock can see the response although he _knows_ John is frowning as surely as if he had eyes in the back of his head.

"John, you're not enjoying this position. No, don't protest. You forget I have data. You don't like being separated from us. You've hardly spoken, which is a significant departure from your normal coital patterns. And I should have realised it before, but you generally find positions in which your partner is facing away from you far less pleasurable. You spend roughly twenty percent the length of time in such positions as you do in those where you are facing Sarah."

John opens his mouth to argue that this position is _fine_ , it really is, but Sherlock continues, "I suspect if Sarah were in the middle then the proportions would work out such that you and I would have eye contact."

John closes his eyes and has to admit _that_ configuration sounds rather nice, yes. Then he realises that the current position can't be all that satisfying to Sherlock either if he's managed _whole paragraphs_ of commentary.

"John, I was enjoying it quite a bit... the only thing lacking was _your_ enjoyment. I understand that the issue is not your attraction to me. You've not had any difficulty maintaining an erection –"

The entire exchange is suddenly mortifying. "Sherlock, shut up. I am not a crime scene. You don't need to deduce me."

"Apparently I do. You were quite prepared to martyr yourself in my backside. Now get down here."

John slides out of Sherlock and makes a quick trip to the bathroom to strip off the condom and wash his hands. He stares in the mirror for a moment, trying to unhear the phrase 'difficulty maintaining an erection' before he returns to the bed. Not only because it _is_ mortifying that Sherlock can be so damned clinical about this, but because John does, on occasion, see men at the surgery with _exactly_ that problem, and he really, _really_ doesn't need _that_ phrase embedded in his brain in Sherlock's deep voice, especially not with all the corresponding visuals.

He curses as he fumbles with the stupid bar of soap. His hands are wet, and he cannot bloody open the paper wrapper, and dammit, he has _very_ important things to attend to in the other room. Any longer and they'll think he's sulking or suffering from performance anxiety.

He has a moment, looking in the mirror in the bathroom, when he feels, well, naked is the obvious word. Awkward is another. Short. Poorly proportioned. Unable to open soap.

But when he returns to the suite, he feels like the luckiest grinning idiot in England. Sherlock and Sarah look _amazing_ together. Sherlock's buried all the way inside her, his hips barely rocking with slow, short thrusts. He looks absurdly tall, even laying down, and for a moment John considers licking a path from foot to head.

Perhaps later when he's a bit more coordinated, less dazed from all of this, and won't accidentally knee his girlfriend in the ribs.

Sarah's head is turned John's direction, and she smiles at him as he crawls across the bed towards her. She's beautiful, flushed with arousal, her hair spilled around her. He lies down against her side, his hand resting on the curve of Sherlock's back. He leans in and kisses her, sloppy kisses more about passion than any sort of precision, especially since her body is moving, movements which John belatedly realises are caused by Sherlock's thrusts. John moans. He has never been this turned on, this utterly entranced by his partners, in his entire life. Cumulatively.

He releases her lips. Sherlock is beginning to thrust a bit faster, and as much as he wants to keep kissing Sarah, it's getting a bit dodgy.

She smiles at him when he pulls back. "I'm sorry, John. I just thought we should have Sherlock in the middle the first time. I didn't really think through the proportions."

"Sarah, it's okay," he says, smiling at her soft, warm consideration.

"Well, yes, but it was your first time with Sherlock and..."

"Really, it's _fine_." She doesn't look convinced so he continues, "Look, this isn't the only time we'll be doing this. We'll get another go."

"Do you _mind_ ," Sherlock interrupts. "A bit busy here."

John half expects to hear that frustrated tone he's so accustomed to hearing in Sherlock's voice, but it's not there. Not at all. No, Sherlock's just been reduced to a mere mortal, his prick begging him to move things along.

"No, of course not. Go right ahead," John answers, grinning as he settles in to watch.

Sherlock makes love to Sarah like he already knows her body. And he does, of course. He knows it from watching John, which is oddly not as disturbing as it should be. At least he's finally taught the man something.

John's not sure what he's supposed to _do_ while he's lying here. If it were anyone else shagging his girlfriend – and John has to stop for a moment when he realises just how alarming it is that phrase _ought_ to be – he would probably chime in to advise on where she likes to be kissed, touched, stroked. But Sherlock has already touched her everywhere John knows about and, of course, being Sherlock, several places John _hadn't_.

He settles for simply observing and accumulating his own set of data for what he's going to do to Sherlock when it's his turn again. He watches Sarah's hands, stroking Sherlock's shoulders, his nipples, his arse. Sherlock's left nipple seems to be more sensitive than his right, and he seems to especially like having his arse grabbed, which sends dozens of images swarming through John's mind.

Sarah's making those short, breathy pants that mean she's going to come soon. He eyes the amount of space between Sherlock and Sarah and wonder's if there's room for him to slip his hand in between them.

"Yes, John," Sherlock says. "Touch her, please. Help me make her come."

He tucks his hand between them, biting his lip to hold back a groan when he feels how wet Sarah is, when he feels Sherlock's stomach brushing against the back of his hand, when she comes underneath his fingers and with Sherlock's cock inside her.

Sherlock has clearly picked up what John likes to think are his best tricks because as soon as Sarah's breath evens out, Sherlock slides his arms underneath her legs, shifting so her ankles are on his shoulders. "John, keep touching her," he grunts, voice strained, as his hips snap forward.

"Oh, God," Sarah moans. "Sherlock... John."

Sarah comes again, head thrashing on the pillow. John has no words for how beautiful she looks. It's as though he's watching her for the first time, free from everything that usually distracts him.

Sherlock's hips slow then stop. He lowers Sarah's legs back to the bed and then crawls out from between them, kissing her before he flops onto the bed beside her.

"Now, John. Please," Sherlock begs.

John has to climb over both of them to get to Sherlock – heaven forbid Sherlock make things convenient for John – and he pauses in transit to kiss Sarah. She smiles against his lips. "Go," she says, nudging him towards Sherlock.

John grabs another condom from the bedside table, and it nearly hurts to roll it on he's so hard. He leans forward to kiss Sherlock, frantic and messy because he wants this now, now, now.

Sherlock pulls his legs up, baring himself to John, and seeing him spread, eyes pleading, nearly undoes John. He positions himself against Sherlock and grabs his arse, which wrenches an ungodly moan from Sherlock. And then John's inside him again.

Sherlock is a genius. This is a thousand times better than it was earlier. John can hear each barely audible grunt Sherlock makes when John thrusts inside him. He can feel Sherlock's legs wrapping around him, pulling him closer. He can see the way Sherlock closes his eyes and tips his head back when John hits his prostate.

"I knew you'd look good underneath me, Sherlock. Fucking gorgeous."

Sherlock's eyes are closed now, and John can see the pride lurking behind the closed-lipped smile spread across Sherlock's face.

"You are. So good. Feel so good. God, Sherlock. I want..." John says, his eyes taking in every possible detail of Sherlock's body.

Sherlock groans. "Tell me, John. Tell me what you want."

"I want everything, Sherlock. Want to see you on top of me, riding me. Want you to shag me while I shag Sarah. Want you... just... want you."

"Yes, John," Sherlock agrees, demands, pleads, rocking his hips now with each of John's thrusts.

John is panting, fighting as his body tries to pull him into another orgasm. He tries to tell Sherlock to touch himself, but words have stopped working. He grabs Sherlock's hand, placing it on his prick.

Sherlock opens his eyes, looking directly at John, as he begins stroking himself. This. Oh, God. This. Sherlock strokes himself three, maybe four times and then he closes his eyes again. Back arched, his sweaty curls in chaos around him on the pillow, he is perfect, gorgeous. His body tenses, tightens around John, and then he comes, sobbing John's name.

John follows seconds later, his voice ragged, his legs burning with exhaustion. Every last nerve in his body stretches, pulls tight, before snapping back as John collapses onto Sherlock, grinning into his shoulder. For several moments, he lays there, catching his breath while Sherlock's ragged pants tickle his hair.

When his heart rate approaches something vaguely resembling normal, he props himself up on his elbows. "Brilliant. God, why is this the first time we've done that?" John asks, kissing Sherlock before he can answer. Sherlock's hands cradle the back of John's head, holding him close, holding him still.

"Forgive me for not just assuming polyamory was on the table," Sherlock says, smiling, when John pulls away.

John realises that Sarah's not in the bed with them, but before he can ask, Sherlock says, "She's in the bathroom."

John's still a bit out of breath as he pulls out of Sherlock and lies down. He really should go grab a flannel to clean them up. Hopefully his legs will begin working again before he passes out. Not likely, actually. As soon as John's head hits the pillow, he knows he's minutes from being comatose.

He hears Sarah walk back into the room and feels the bed shift when she kneels next to Sherlock.

"Oh, thank God," Sherlock mutters, and John leans up to see Sarah running a flannel across his stomach. "John, your girlfriend is a saint."

"Our girlfriend," John corrects.

Sherlock lets out a strangled half-giggle before Sarah's kiss cuts him off. John watches for a moment before his eyes drift shut again.

"You two," she says, now leaning over John. Warm flannel. Yes, definitely a saint. He pulls her down for a kiss. "You two are welcome to do _that_ any time. Any time at all, so long as I can watch."

John is grinning as he falls asleep.

**Notes for the Chapter:**

> A million billion thank yous to the alpha/beta/Britpicking armada who've helped launch this story: Annietalbot, Christev, cyanide_faery, machshefa, and Sc010f. *continues to abuse naval metaphors*


	5. J (Juliet) "I am on fire and have dangerous cargo on board: keep well clear of me"

The three of them are crumpled into an exhausted heap. Sarah and John are dozing, half-asleep and tucked on either side of Sherlock. He idly strokes his fingers along their backs.

Sherlock stares at the ceiling, trying to assimilate all of the disparate bits of information they've thrown at him tonight. Since the cab ride, since the flat, really, his brain has been so muddled by endorphins and arousal that he hasn't accomplished anything beyond the most obvious observations, almost blindly following where John and Sarah have led him.

But it is quiet now. Just the sound of the three of them breathing. Plenty of time, plenty of silence for thinking.

Even as John sleeps, he is relentless in his affection, his arm thrown across Sherlock's chest. Today isn't the first time John's touched him. It's not even the first time John's touched his bare skin. But it all _means_ something now, this touching. Sherlock can't put words to what it means, no. But he's vaguely, suspiciously aware it points towards words he never thought he'd have any use for. Words he'd nearly deleted from his vocabulary.

John shifts, his fingers moving to Sherlock's shoulder. Sherlock rewinds to all the other times John's touched his shoulder. Has this attraction always been there? Did he not notice it because he's so single-minded? Or did his subconscious know and its verdict got tossed out with everything else he deemed irrelevant? Or is this new context warping his perceptions of their interactions over the course of their friendship?

This... entire arrangement is unexpected. He never thought... never suspected that John and Sarah would want _this_. Even now that he knows the exact chain of events that led them _here_ , it doesn't seem possible that Sherlock Holmes, man who knows fuck-all about relationships, is suddenly in the very centre of one, flanked by John Watson and Sarah Sawyer. And they are all naked.

It's like the punchline to a stupid joke or one of the dreams in that asinine book he'd read when he was eight after someone suggested that when he slept his mind would go on thinking, revealing answers in the form of dreams. Utter shit, of course. And Sherlock has never once had a dream where he showed up at university or a crime scene naked as the book suggested was common, _normal_.

Sherlock frowns. His mind is wandering. Not desirable.

John shifts against him again, his breath ghosting across Sherlock's skin. Sherlock shivers. Damn it. Molecules of John's carbon dioxide waste should not have such an impact.

He can feel where Sarah's hair tickles his arm. Where John's leg is thrown over his. The way Sarah's vertebrae slide under his fingers.

He should not be enjoying these sensations. Sensation is distraction.

But he _is_ enjoying it. Just hours into this _relationship_ , he could not give up the feel of their bodies pressed against his skin. The feel of their hair, their breath, their heartbeats.

Their heartbeats... John's resting heart rate is too high. Perhaps Sherlock needs to orchestrate more chases across the city to help his – his mind stumbles over what to call John... flatmate is inadequate now... lover? partner?

Sherlock silently curses. His mind has wandered off again. The word _distraction_ is apparently far more inadequate than _flatmate_.

John moves again, _nuzzling_ against him. He'll be awake soon. Both of them will be.

Sherlock continues to think while his relationship sleeps.

It is unfathomable that they want to share all of this with _him_. He doesn't _fit_ with their murmured endearments, their intimacy, their happy domestic bliss. And yet it seems he does. One twenty-minute conversation and he let John crawl into his lap, let them pull him into this relationship like he was some sort of missing piece, hiding in the sofa waiting to be found.

And find him they did. Found parts of him that hadn't been exposed in years, hadn't been touched. Though at least he's not shocked with discovery that he enjoys having the pleasure centres of his brain stimulated. Even his experimental fumblings had shown him that much. They'd simply demonstrated that it wasn't worth the trouble of seeking out other people to stimulate them. Far less trouble just to do it himself.

But with John and Sarah it _doesn't_ seem to be trouble, which is alarming in itself. John had chastised him earlier for the earlobe thing, yes. But even that is understandable, easy now. Sherlock can accept – well, logically, practice may be another matter altogether – that there's a different code of conduct for these situations.

It's the research. It all goes back to his research. He's processed everything he'd seen when he watched John and Sarah. He's put names to what he observed there. Words like trust and vulnerability. And it's the vulnerability that makes it easy to accept John's code of conduct.

Because he can see it. Can see now that when you're connected with someone else like this, when you're crawling inside each other's skin, it would be all too easy to cause irreparable damage. To tear at people. Hurt them. He can think of single-syllable words that might destroy him if they were uttered here.

John knows every centimetre of him now. Knows all the soft spots. All the weak spots. John has held Sherlock in the palm of his hand and has spread Sherlock open with his fingers. He knows all (well, many) of the spots that, if proper pressure is applied, will make Sherlock beg and bargain and offer things that no one, least of all Sherlock, in their right mind would offer.

And with that data in hand, he has done nothing but lavish attention, setting his own pleasure aside for Sherlock and Sarah's. It is disturbing.

But it is more disturbing that John and Sarah have replicated, back at the flat and in this hotel room, those same facial expressions that drove Sherlock to sit outside John's doorway. They've replicated those expressions while they were looking at _him_ , and it is at once terrifying and exhilarating. He wonders what his own expression might have been at the time. He suspects he knows. He suspects it looked shockingly similar to theirs, but that is not something he can process right now. It is too... enormous, overwhelming, unprecedented, unexpected.

He sets it aside for later analysis.

John shifts, close to wakefulness now.

Sherlock breathes. Slow, focused breaths. It won't do to panic over this. There's... there's actually nothing to panic about. Sherlock _trusts_ John. Trusts him in ways he's never trusted anyone.

It's _their_ trust that is so terrifying. John and Sarah trust Sherlock not to shred them into tiny pieces with his own set of data. Not to utter the one-syllable words that would break _them_.

And this trust... for the first time, Sherlock knows he's found something that's too irreplaceable to experiment with. Too precious to disassemble to investigate how it works. Because he's certain he wouldn't be able to put it back together if he broke it, which he inevitably would do.

Sarah rolls over, now nestling against Sherlock's side.

Sarah.

If Sherlock squints at the data, filters it just _so_ , then he can almost fit John's interest to it. But Sarah is a complete mystery. He welcomed John into his life. But Sarah... Sherlock had only grudgingly tolerated her after not even Moriarty's interference could pry her from John's side.

She finds him attractive. The physical evidence confirms that. But it's more than that. She had placed Sherlock in between her and John, even though anyone with half a brain could tell the angles were all wrong there. And she _is_ smart, clever even on occasion. She just doesn't broadcast it, purposefully conceals it sometimes. Many times, it seems.

No, none of this makes sense.

It defies explanation and it is fascinating.

John wakes, and he stretches and looks up at Sherlock, that innocent smile of his spreading across his doughy, sleep-ridden features.

Sherlock smiles back at him, if a bit nervously. No one has woken up next to him before, and it's entirely foreign that John is happy because of it. He half expects John to be speaking in tongues when he opens his mouth.

"Well, it's nice to see you're still here. I thought you might have decided you didn't _do_ relationships while I was asleep," John says, his eyes searching across Sherlock's face.

"I can't say I really comprehend this. But I'm still here."

John is completely still under Sherlock's arm. His eyes are filled with concern, worry, and it is, again, completely befuddling that he would feel that way about _Sherlock_. He asks, "And will you still be here? Once you figure it out?"

"I don't think I will _ever_ figure this out, so it seems I'm not going anywhere," Sherlock answers, forcing a small smile.

"Good. That's good," John says, tension ebbing from his features.

He shrugs out from underneath Sherlock's arm and flips over, pinning one hand on either side of Sherlock's head. His head lowers, his lips brushing across Sherlock's. Sherlock has never been kissed like this. It's not powered by lust or physical attraction, this kiss. It's not as noisy as that. It's a quiet, gentle kiss, and it's over before Sherlock can ascribe any other descriptors to it.

Sarah's awake now, too; her arms have tightened around him. "Hello there," she says, scooting up the bed so that she can kiss him. Affectionate is the word that springs to mind when her lips press against his, once, twice.

Then she leans over Sherlock and kisses John. Sherlock stares at them. Both of them. They both share affection without effort, like it's more difficult to withhold it than deliver it. He is entirely out of his element.

John and Sarah stop kissing. They're smiling too much to continue. They're both looking at him now, and Sarah asks, tone teasing, inviting, "Like something you see, Sherlock?"

"Just comparing the way both of you kiss me to the way you kiss one another," he answers, hoping they don't ask him to enumerate. He's not sure he could offer any... well, any observations aside from the most obvious. _Is it a matter of not knowing what I prefer? Will their kisses change when we've all been together longer? _, he thinks, ignoring the part of his mind that's harassing him for spending _this long_ contemplating _kissing_.__

"More data?" John asks.

"Always collecting data, John," he responds, punctuating his sentence by trailing his thumb down the side of Sarah's neck. She shivers.

"You really were just gathering data while you were watching us, weren't you?" John asks, his thumb idly brushing across Sherlock's nipple. The sensation is an echo of the pleasure he felt earlier. Curious.

Oh. John's question. "Well, yes," Sherlock answers, hoping that John doesn't dig further, doesn't inquire about the underlying question driving the investigation. This is all too new, too overwhelming to reveal _that_.

"You didn't, you know... get off? Not even once?" John asks.

It takes a moment for Sherlock to parse John's slang. Mercifully, he's steered the conversation in a wholly predictable direction. "Oh, I see. You think I'm a voyeur. No, no, I'd much prefer to participate. Sorry."

"Why are you apologizing for not being a voyeur?" Sarah asks. "Surely after all that you don't think we only wanted you to watch?"

"Well, no... But John's an exhibitionist."

"No, I'm not," John says, brow furrowed.

How could he have got that wrong, Sherlock wonders. "What do you mean, you're not?"

"I mean I don't get off on people watching me."

"But you _got off_ on me watching you... and you didn't tell Sarah about it because you were afraid she'd stop you. And you started doing all those positions..."

John interrupts his string of evidence, "I got off because it was _you_ watching. And I didn't want to tell Sarah at all. I knew she'd be interested, and I didn't want to cheat her out of the thrill of seeing you out there for the first time."

Sherlock cannot breathe. He looks at Sarah who simply shrugs at him, smiling. "You knew she'd be interested? You'd discussed this?"

"Sherlock, I'd have to be a _complete_ idiot not to realise my girlfriend was attracted to you."

"Oh," Sherlock says, the gears in his brain churning and beginning to pick up speed. Sherlock wonders if there's a word for exactly _how_ oblivious he's been. They are both staring at him, smiling, and it is unnerving, like being an ant under a magnifying lens in July.

Sherlock redirects the conversation. "And the positions? Were you just showing off then?"

"Well, I suppose I hoped I'd eventually find one you liked enough to join in," John answers, his tone at once serious and coy, teasing.

Sherlock takes the latter interpretation and runs with it, teasing back. "So, you were trying to... seduce me with your callisthenics? What, was that some sort of... sexual semaphore, John?"

John starts laughing first, but in seconds, the three of them are laughing together. Sherlock laughs a bit longer than he ordinarily might, his mind racing as he flips back through the evidence, wondering what else he's misinterpreted. He never sees the two of them interact with other people, well, not socially. Perhaps if he had, he'd have noticed they treated him differently? With interest? With affection? How could he not have seen _this_?

"Sexual semaphore," John says, grinning and setting off another round of giggles. "I suppose it was. Well, we're both idiots, aren't we? Thank God we've got Sarah around to figure things out."

There's another round of smiling kissing. Utterly bewildering, it is. And yet his body seems to crave it.

John is grinning when he says, "Still, it's too bad nothing caught your attention. We could have by-passed that nasty sulk you worked yourself into."

Sarah looks at John warily, as though he's just said something that will upend everything. But Sherlock laughs, and his new lovers look at him in utter confusion. Oh, John mentioned something about Sherlock's sulking. Perhaps laughter wasn't an appropriate response.

"It's just... you would have looked utterly ridiculous making the signal for attention during sex," Sherlock explains, setting off another round of his own laughter at the image.

They are still not laughing.

"You actually know semaphore," John says, familiar disbelief in his tone, but Sherlock can hear the affection and can feel the curve of John's lips when he presses them to Sherlock's temple.

Sherlock swallows the enormous lump that's settled in his throat. "Cyphers, John. Very useful."

"Well, what's the signal for attention look like, then?" Sarah asks.

"It involves waving your arms up and down, roughly from the –"

"Show us," John says.

"This bed is comfortable. I'm not getting out to demonstrate semaphore."

John's index finger pokes Sherlock's rib repeatedly.

"Damn it, John."

"Go on. Get up. You're all the time having me do ridiculous things for you," he says, still poking.

He grumbles and climbs over John and stands beside the bed. John and Sarah watch him expectantly. "Oh, I am _not_ doing this naked," he mutters before stalking to the cupboard. He retrieves the complimentary dressing gown, tying the sash firmly around his waist. It is thick towelling, and Sherlock feels... padded, like he's been wrapped in a duvet.

He returns to the side of the bed, grabbing his and John's underwear along the way. "Ordinarily these would be square-shaped flags, bisected by a diagonal line, one half would be yellow, the other half red." He raises his left arm to eight o'clock and his right to four o'clock, checking that the angles are correct and experimentally raising his arms to ten and two, respectively.

"Right, I'm John Watson, expert in the art of seduction via semaphore," he announces, ducking John's horribly aimed pillow.

The dressing gown flaps as he rapidly raises and lowers his arms.

John and Sarah are both laughing now, and Sherlock finds it hard not to be delighted that the three of them share a joke of his making.

He launches himself back between them, not bothering to get under the covers. They'll want to order room service soon since John didn't eat his meal earlier, so someone will need to go to the door. And God knows, _Sherlock's_ not an exhibitionist.

John and Sarah curl into him, their heads resting on his shoulders and their hands clasped together on his stomach. It is at once suffocating and the most content he's felt in his entire life.

**Notes for the Chapter:**

> My enormous and undying thanks to my alpha and beta team: Annietalbot, Christev, Machshefa, and Sc010f. And extra thanks to red_adam for the last minute Brit-pick.


	6. A (Alfa) "I have a diver down; keep well clear at slow speed."

John and Sherlock are bickering over the room service menu, and Sarah is quietly amused that they have both reverted to form. They're standing by the phone, John naked with his arms crossed and Sherlock engulfed by the white, fluffy, hotel dressing gown.

Sherlock is holding the menu, dangling it out of reach when John grabs for it. "Just let me order for us, John. I won't get anything that you both don't like."

"Sherlock, I can order my own food, and so can Sarah," John says in his trademark 'I am not a moron' voice. Sarah adores John, she does, but it does not seem he is ever going to learn that _that_ voice simply makes Sherlock all the more determined to illustrate precisely how wrong John is.

"Were you planning to avoid excessive carbohydrates? No, you weren't. They'll make you sleepy and sluggish, which is entirely unacceptable given the circumstances."

John scowls. "We are both doctors, you know. We know how basic digestion works."

"Were you or were you not going to order the curried potatoes?"

John huffs, and when Sarah laughs, he glares at her for a moment before conceding defeat. "Fine. Order," he says, his annoyance dissipating.

He tackles Sarah, pinning her arms above her head. "Amused by that, were you?" he asks, grinning as he takes her wrists in one hand and tickles her with the other.

She shrieks with laughter as she tries to simultaneously wrench away from John's fingers and free her wrists. Sherlock, help!" she cries through her laughter.

Sherlock rolls his eyes at them and turns around before picking up the phone.

She and John both giggle at Sherlock's response, their sides heaving. John's smile wanes. He lets go of her wrists and glances over his shoulder to look at Sherlock, back still turned, ordering their dinner. John's face is so open, so honest when he looks at her again. "Are you doing all right with all this?"

"Quite. And you?" she asks, wrapping her arms around him.

"Mmhmm." John trails kisses up her neck, stopping just below her jaw. "I love you," he whispers.

Sarah kisses John as she blinks back tears. She ignores the little voice telling her how sappy it is that she loves John more today than she did yesterday. Kissing him feels so different now, whether it's just the contrast between him and Sherlock or whether it's because of the shift in their relationship, the adjustment from two to three making this quiet moment between just the two of them all the more intimate.

John pulls back, smiling at her before he glances over at Sherlock, who has abandoned the phone and the ordering for one of the chairs in the sitting area. He's squinting at his mobile, scrolling through something, and Sarah feels John's body go rigid.

"Sherlock! Here? Now? Really?"

Sherlock looks up, startled. "What? This is... relevant," he says, gesturing at the mobile.

"What could _possibly_ be relevant now, Sherlock?"

"Data, John."

Sherlock's eyes flicker to Sarah, and she _feels_ him observing, hypothesizing. Her breath catches. Then his attention reverts back to his mobile. She may not survive whatever Sherlock is researching.

"Right then. Scroll away. Wouldn't want to stand in the way of data gathering," John says, turning _leer_ at her.

Sarah shivers. The team of Holmes and Watson has turned its sights on her, and she wonders if _this_ , this mix of terror and adrenaline and exhilaration, is how London's criminals feel when they've got Sherlock and John on their heels. Granted, Sherlock and John have far more pleasurable things in store for her, but it is overwhelming to be the focus of their attention.

And she may never be able to hear the word _data_ again without blushing.

John kisses her again, languid, lazy kisses that go on for ages. Sherlock keeps glancing over at them, and it is dizzying, seeing him over there, seeing him watching, knowing he'll be joining them later.

Someday, not any time soon because she wants to hold on to the fantasy just a bit longer and because Sherlock needs to be secure in how much they want him and how much he means to them, but someday... someday she'll ask him to stand in the hallway outside John's room and watch them again.

Their kisses, her thoughts, and the images her mind's projecting of John and Sherlock together all wrap around her, stoking the desire, the arousal that's been smouldering for weeks now.

She reaches down to stroke John, and he chuckles into their kiss. 'Really, that's flattering, but I think I'm out of commission for a bit. Although, I think after dinner Sherlock and I will manage to keep you entertained,' he says, running his fingers up her thigh.

John swallows her whimper with another kiss as his fingers continue teasing her.

It's almost a relief when there's a knock at the door and Sherlock walks across the room to wheel in the room service trolley. He tosses two dressing gowns onto the bed, and she blushes because the room surely hadn't come equipped with three. If the front desk didn't suspect anything before, they certainly do now.

Sarah flinches when she sees Sherlock lifting lids to reveal the truly decadent foods hiding underneath. Tonight – today, really, if you include the shopping – is going to cost a small fortune. It's worth it, of course, worth every last pound. But next month's credit card statement will be enormous.

Sherlock hands her a plate and her mouth waters. He ordered perfectly, he really did, and she marvels for a moment that he knows her preferences _this_ well. She carries her plate over to the sitting area, and even though she ate her fill at dinner, she is suddenly starving.

She slices into a beef medallion, dredging it through the sauce, and takes a bite. Cherry sauce. Yes, next month's statement will be worth it.

Sherlock interrupts her thought, "So, no one won a free night here, then." He looks smug.

"How," John begins, "could you _possibly_ deduce that from the room service trolley and miss the fact that we wanted to shag you rotten?"

Sherlock had opened his mouth to lay out his logic, but his mouth snaps shut as John finishes. He sighs. "I've already told you, John. No evidence of past polyamorous relationships in your background eliminated it from the solution set."

John rolls his eyes, but he's too distracted by his plate to argue back. They are all distracted by the food; even Sherlock is attacking his plate with gusto.

The only sounds are the clink of cutlery and satisfied moans. But at length, Sherlock interrupts the silence, "You know, John, you really ought to have used International maritime signal flags instead of semaphore."

"I think from now on, I'll just proposition you directly, thanks," John answers. "Fine, I'll bite. Why?"

"Well, the alphabet consists of a set of 26 individual flags. There's no possibility of anyone misinterpreting because one's arm angle is a bit off."

John glares at him, but Sherlock soldiers on.

"They correspond to the NATO alphabet, so technically each is a letter and a word. In addition, each flag has a meaning... many are appropriate to this situation, I think."

"Such as?"

"Well, I'm trying to decide the best one to lead with," Sherlock says, stifling laughter.

He is – and Sarah cannot believe she's thinking this – adorable. She has seen Sherlock laugh more times this evening then she has cumulatively since she's known him. And now, _now_ she gets to be in on the jokes he and John share.

"Zed. Zulu. I need a tug."

John snorts. "Sherlock Holmes, you are a very strange man," he says, dipping his head as he shakes it and attempts to hide the enormous smile spreading across his face. "Oh, God. You're going to do this to me at crime scenes now, aren't you? You are. You're going to sneak up behind me and whisper 'Q' in my ear, and I'll have to think a moment to remember what it means, and then I'll be leaning over the body, giggling like an idiot."

Sherlock laughs so hard he nearly tips his plate onto the floor.

"Bugger. What does Q mean, then?"

Sherlock is _still_ chuckling, so Sarah answers, "Quebec. My vessel is 'healthy" and I request free pratique... license to enter port with the captain's assurance that the crew is free from contagious disease." She grins at Sherlock when his entire body twists as he looks at her. "My grandfather had a boat. I had no _choice_ but to learn maritime flags."

"You knew. You knew the semaphore too, didn't you?" Sherlock asks.

He squints at her, assessing her, likely trying to figure out all the other things she's known and never mentioned. He will never again assume that she isn't following along, that she doesn't already know the answer to the question she's asking. Although when he runs the scene through the entirely accurate playback machine that is his brain, he'll also realise that she didn't _have_ to explain what 'Q' meant, didn't have to reveal her hand.

"Maybe," she finally answers. "Does that bother you?"

He thinks for a moment, spearing a citrus salad that Sarah is _certain_ was not on the menu. "November," he answers.

"No," she translates for a confused John.

Sherlock grins, and the rest of dinner is punctuated by Sherlock answering all of John's questions – not hers because she begins rephrasing them after the fourth aggravating response – with 'November' or 'Charlie'. Eventually, John threatens to lock Sherlock in the bathroom if he doesn't begin using proper English.

And he nearly does, except he realises Sherlock _is_ answering all his questions and decides to press his advantage.

"Were you responsible for destroying my favourite socks, that damage you blamed on the laundromat?"

"Charlie."

"I _knew_ it. Bastard. And my jumper?"

"November."

"Ah. Well, that's a bit unexpected," John says before taking a bite of what looks like duck with orange sauce. John's favourite. His favourite which he never orders because he always baulks at the price, usually opting for Lo Mein instead.

They eat in silence for several moments, but soon enough John's figured out how to phrase the questions he _really_ wants to ask.

"Did you enjoy watching us back at the flat?"

Sherlock is caught off-guard. He clearly didn't expect John's silly line of questioning to take this route. He considers his answer for a moment, before he says, "Charlie."

"Did you ever consider joining us?"

There's another long pause. "November."

John mulls over Sherlock's answer. "You weren't just gathering data, were you?"

Sarah wonders if this is going to be the question that ends their game. But at length Sherlock answers, "November."

"Will you tell us why you were really watching?" John asks, his tone serious, but not demanding.

"November," Sherlock answers without thinking, but he is terrified, cautious, will barely look at John.

"Sherlock, relax. I'm not going to force it out of you."

"Oh," Sherlock says, tension rolling out of him, and it takes her a full minute to realise that he's said 'Oh' and not 'Oscar' and there's no need to translate, although 'Man overboard' is certainly fitting here.

Sarah lets out a breath, forcing herself to relax. As exciting as all of this is, the newness of it, the excitement of having a new partner, of having _Sherlock_ , she _cannot_ wait for things to get settled. For all of them to stop being so jumpy, so sure that at any moment someone's going to say something that makes everything explode.

The remainder of dinner passes without incident. Although somewhere between the main course and the dessert that Sherlock declares will be easier to eat in bed since they're sharing dessert, though how it's easier she's not sure because they've each got a hand inside her dressing gown, and this chocolate torte really deserves more attention than she's able to give it... somewhere during all of that John devises some sort of threesome calculus wherein the fact that he and Sherlock have each come twice means she should have come at least four times. It makes no sense, but she isn't about to argue, especially when Sherlock _licks_ the back of his dessert spoon in a way that ought to be illegal.

After dinner, _Sherlock_ insists that they pile the dishes back onto the trolley and Sherlock pushes it out into the hallway. It wouldn't do to be interrupted should they return to retrieve it, he argues, which might be the flimsiest excuse she's ever heard, but he and John have somehow, without speaking, without texting, planned _something_.

John strips off her dressing gown, trailing scorching open-mouthed kisses down her neck. He stops to shed his own dressing gown then props himself against the headboard and pulls her so she's nestled between his legs, slumped against him. John's lips are on her neck again, sucking, licking, as Sherlock walks towards the bed. She is breathless, as though the wind's been knocked out of her, even though John is being achingly gentle.

Sherlock stands at the foot of the bed for a long moment, watching her. And her heart stutters as she wonders if he _knows_ , if he's figured out exactly what it's doing to her. But his expression is missing that satisfied gleam of having deduced something well-hidden. No, he's still observing, calculating. And then he crawls between her legs, licking and kissing his way up her thighs.

Oh, God.

Sherlock's hands are framing her hips, and she spends a long moment staring at his fingers. His long fingers that she has seen plucking at violin strings. Oh.

He's stopped kissing her thighs, and she looks away from his hands to find him staring at her, the corners of his mouth tugged up in amusement. And then he drags his right hand down her hip and slips one, then two fingers inside her.

John has not stopped touching her, kissing her, and yet she's completely forgotten he's there. So she jumps when he says, "I love watching Sherlock's fingers fucking you, Sarah. Do they feel good?"

Her ability to form rational thoughts is not going to survive this endeavour. Between John's filthy commentary in her ear and the sight of Sherlock – who is now dragging his tongue closer and closer where she _wants_ it to be – between her legs, she's going to be lucky to be able to string syllables together at the end of this, much less sentences.

"Do they?" John repeats.

"Yes," she whimpers.

And then Sherlock – Sherlock who is brilliant and who needs to post whatever web sites he found on his mobile earlier, needs to publish them on his blog, because whatever they were, they were bloody effective – flicks the tip of his tongue across her clit just as he crooks and presses his fingers inside her and she is gone... gone... swept away by John and Sherlock, awash in every kiss and suck and touch.

It is all a blur of touch and sensation until some number of orgasms later when John asks her how many times she's come, as if he and Sherlock are going to record this and attempt to break their record in the future. Has it been five? Six? Does it even matter once you get above three?

"Five," Sherlock answers, lifting his head for a moment. "I'm going to try for six."

His voice is so matter-of-fact, so clinical, so arousing. Though it is mildly terrifying that Sherlock has become _fascinated_ by the female body's capacity for multiple orgasms.

And she's honestly not sure who's enjoying Sherlock's fingers more, her or John, who has not ceased _talking_ about Sherlock's fingers and what they're doing to her and how her body looks. She would tell him to shut up because he sounds how she imagines it would sound like if directors did commentary tracks for porn, but it sounds hot and filthy and amazing because it is _John_ who's watching her, who's providing the constant stream of audio feedback.

And all the while, Sherlock's fingers are deep inside her, twisting and curling. He is going to murder her with his detailed study, with his tongue.

John's hands are everywhere: her breasts, her arms, her belly. She gasps when she looks down and sees his fingers trailing over Sherlock's. They're both clutching her hip. This... oh, God, this is overwhelming. It's hot as hell to watch _anything_ they do together: touching, kissing, fucking.

But this... it's more than that. Seeing their hands joined on her body, it's... she's never felt this close with anyone, not even with John before now, before this.

She feels every millimetre of skin where they're touching her. She is surrounded by John, covered by Sherlock. She wants more, wants everything, wants this feeling, this room to last forever.

And then she's coming again, jerking in John's arms as he holds her even closer, tighter. It is wonderful and agonizing, and she is flayed open, vulnerable, sensitised, raw.

She is sobbing when her orgasm recedes, leaving behind a jumbled pile of overloaded nerves.

"God, Sherlock, stop. I can't... no more," she begs.

Sherlock presses kisses onto her thigh, and she feels his fingers slip out of her.

She is exhausted, her hand, her entire body leaden, but she reaches down to thread her fingers through Sherlock's hair as he pillows his head on her thigh. He leans into her touch and she smiles.

"Come here," she tells Sherlock, opening her arms to welcome him. He shuffles up the bed and settles between her thighs, into her arms, his height making it so his head rests against her shoulder.

Sarah closes her arms and holds onto him, presses a kiss into his hair. John shifts so that he has one arm wrapped around each of them, his fingers stroking along their arms. She turns and tilts her head to look at John. He is _beaming_ , and they share a messy, awkward kiss before her neck begins to ache.

She is smiling, and she can feel John grinning against her neck. They are both giddy with their new found freedom to show Sherlock how much they love him. Neither are quite brave enough to mention it, of course. But they do love him. They'd never have welcomed Sherlock into their bed if they didn't. But at the moment, verbal reassurance is right out because Sherlock is still alternately wallowing in and being spooked by their affection. At once craving it, while occasionally looking like it's going to bite him.

So it seems like a minor miracle when Sherlock twists and levers himself so he can kiss John over her shoulder. Their breath is hot in her ear, and for once, she doesn't mind. She closes her eyes and listens, hears John pant, _feels_ them moan _around_ her, feels how hard they are, pressing against her.

Sherlock's hand snakes up her body, his thumb brushing across her nipple. And she really wishes Sherlock had stopped at number five because the sixth nearly broke her. While the invitation is very, very enticing, it will have to wait because she is so thoroughly wrung out. She intends to enjoy their next attempt at an actual threesome when she's certain she'll stay awake through it, when her entire body isn't drowsy.

So she pries herself out from between them, flattered by the twin set of disappointed moans. "Sorry, but I'm out this round. Maybe after I can feel my limbs again."

John actually pouts at her. But then Sherlock's tongue swipes across John's lower lip once, twice, before Sherlock sucks John's lip between his own. She's fairly certain John forgets all about her after that. They kiss for ages, and she can see their tongues slide against one another as the kisses grow progressively sloppier.

She props herself on her side, gathering half the mountain of pillows to support her and watches as Sherlock tugs John down the bed, his hands eager, roaming over John's body. They moan as Sherlock's hips settle between John's legs, and Sarah is mesmerised by watching them move together, thrusting against one another.

When Sherlock reaches between them to slide his hand around their cocks, John bucks his hips and cries out, "Oh, God, Sherlock. Oh, yes."

He is writhing under Sherlock's touch, his eyes closed and head thrown back into the pillow as Sherlock very nearly devours John's throat, John's chest, John's cock as Sherlock's hands dart over whatever areas his lips have abandoned.

Sarah's overwhelmed at the sight of them, finding herself wondering _when_ she'll stop thinking about how much more she loves them, as if her affection for them is on some sort of exponential, boundless climb.

And now she's blinking back tears. The jagged knife of Sherlock's attentions truly ripped her open and gutted her earlier: she is _never_ this emotional. And she is glad she bowed out of this round because she would be sobbing and blubbering out endearments that would certainly send Sherlock tearing out of the room. .

It is no small victory that they've got him this far without him doing a runner, deciding this is all too much. For all of Sherlock's data and his very clear, very thorough understanding of the physics and anatomy involved in intercourse, he's been wholly overwhelmed by the actual intimacy. When they woke up earlier, he'd been frozen while she and John kissed him, looking as though he was afraid that if he so much as moved the wrong way it would all be over.

But he had relaxed over the course of dinner, channelling whatever nervous energy he had into his exhaustive abuse of all things naval. He had slowly unwound, leaning against them, touching their arms, as if he'd finally realised he had the freedom to touch them as much as he wanted to. The emotional intimacy will come with time, once it sinks in that they love him for who he is, not who they want him to be. But at least he's made the leap to physical intimacy, not just the sex, but the freedom to touch, to hold.

 _Or perhaps the emotional intimacy will arrive sooner rather than later_ , she thinks as she continues watching Sherlock as he _adores_ John, lavishing, no drowning him with affection, his eyes never once leaving John's face. It is so very clear that Sherlock loves John, that he's pouring all of his feelings for John into this moment.

John groans as Sherlock takes one last suck and pulls his mouth off John's prick. Sherlock grins at John for a moment, and then his eyes meet Sarah's. For a heartbeat, she simply studies him, smiling at the joy dancing in his eyes.

"Are you enjoying the show then?" Sherlock asks, his mouth quirked and eyebrow raised. She's seen this expression a thousand times, but never when it was barely smothering an enormous grin that tugs at the corners of his mouth, threatening to take over.

"Quite," she says and props herself up so she can kiss him. His lips slide against hers, and her stomach somersaults when he sucks on her lip. "Oh," she gasps against his mouth. His tongue slips between her lips, flicking against her tongue.

John moans from stage left, and Sherlock pulls away from her, whipping his head towards John. "Impatient, are we?"

"Well, yes, but... that was just... hot."

"Oh," Sherlock says as his eyes flicker to Sarah. A ghost of a smile creeps into his expression. "Well, let's get on with things, shall we?"

Sherlock reaches over to grab the lubricant from the bedside table. All three of them watch as he squeezes out a drop and rubs it between his thumb and forefinger.

She and John are never going to be able to look at Sherlock's hands again in public.

Satisfied with the lubricant's properties and seemingly oblivious to the attention he's drawn, Sherlock applies a liberal strip onto his fingers and distributes it over them. He looks up to find his new partners riveted. His face flushes, and for a moment he looks inordinately pleased with himself.

Then Sarah watches Sherlock's fingers disappear between John's legs. John apparently _is_ impatient because he begins thrusting against Sherlock's fingers the moment they dip inside.

"That's... good. So good," John says, groaning every syllable as his feet dig into the mattress.

All Sarah can think about is how next time she wants to be the one to prepare John. She wants to press her fingers inside him, eliciting the same whining moan that she has _never_ heard John make before. She wants to be the one to make him twist and push and _beg_ because it's not _enough_ and please won't someone touch his prick.

She looks up to see Sherlock watching her, taking note, and she shivers, knowing she won't need to ask next time. She'll be volunteered for the task.

Sherlock declares John ready and climbs off the bed, muttering about flannels and being prepared for this round. She and John grin at one another as Sherlock leaves. "You all right by yourself over there?" he asks.

"Never better," she replies, her smile growing even wider when Sherlock returns.

Sherlock climbs onto the bed as he grabs a condom from the bedside table. Sarah watches him roll it on, squirming a bit as she remembers him doing so earlier, remembers the feel of him between her thighs, remembers what it was like to have him peering down at you, eyes half-lidded.

Sherlock's eyes slam shut as he slides inside John, clutching at his hips as if he might not stay anchored otherwise. His eyes stay shut until he's all the way inside John and John has clasped Sherlock's hands underneath his own.

Then Sherlock begins moving. They are beautiful to watch, completely spellbound and wrapped up in one another, and Sarah finds herself wanting not to even breathe loudly for fear of intruding. She wonders if this was what it was like for Sherlock to watch her and John, if he could see their love for one another radiating in their expressions.

"God, you're amazing. Been wanting this for ages," John pants.

Sherlock's looks surprised, and as John continues his extolling his virtues, Sherlock's expression shifts from disbelief to flattered and ends at flushed embarrassment when John babbles for at least a minute about how good Sherlock's cock feels inside him. "Does it feel good having your cock inside me?" John asks.

"Yes," Sherlock says, confusion creeping into his features.

Not stymied by Sherlock's reticence, John follows up with _more_ questions that earn him monosyllabic responses. Sherlock is biting his lip, likely seconds from telling John to shut up when John slides his hand up Sherlock's chest and pinches his nipple.

Sherlock lets out a strangled groan and practically launches himself forward so he can kiss John. There is absolutely no finesse to the kiss, and Sarah smiles as her lovers maul one another. John's fingers are unrelenting on Sherlock's nipple, and every time he pinches, Sherlock nips at John's lower lip.

"Oh, God. Stop, John," Sherlock begs.

"Why?" John asks cheekily, and Sarah snorts. Sherlock may not know it, but he's about to be retrained. John usually considers his filthy sex talk a duet performance. And he's not shy about directing, either.

Sherlock closes his eyes and swallows as his hips stutter to a halt. "I should think it would be obvious even to you, John."

"Hmm. Hardly a good idea to throw veiled insults when you're in a compromising position."

Sherlock's eyes narrow, and he responds, "Traditionally it's the individual on the bottom who's–" Sherlock's voice ends in a strangled sort of whimper.

John's hands haven't moved, and Sarah tries not to grin when she's realised what John's done.

"Tell me," John says, his voice husky, barely a whisper, somehow inviting rather than bossy.

"It felt too good."

John apparently relaxes because what looks like relief flashes across Sherlock's face and Sarah hears him sigh.

"And?" John says, sneaking a hand up Sherlock's chest again.

Sherlock tries to glare at John's hand, the venomous look that normally lurks in his eyes completely fogged by lust. "I believe you said something earlier about manipulation having no place in the bedroom."

John slides his hand to Sherlock's side. "Neither does holding back. Look, you don't need to be as filthy mouthed as I am if that's what you're fussed about. Just... please. I want to hear you. You can ask questions if you'd rather. And, yes, I know I can't tell you anything you don't already know," John rambles, his apprehension evident.

The details shift into focus and Sherlock visibly relaxes, shoulders dropping as he exhales. "You find my voice arousing and want me to talk to you."

"Voices in general, yours in particular, yes."

Sarah bites her tongue to keep from grinning. John has just armed Sherlock, and Sarah can already imagine their bickering when Sherlock uses his voice to his advantage in the future.

"And you don't care what I talk about," Sherlock asks, beginning to move inside John again.

"As long as it's on topic," John responds, breaking off into a moan.

"So if I deduce your–"

"No! No deductions. Strictly observations. Pleasurable observations. You know what, it's fine. You don't need to talk."

Sarah has never seen anyone glare so petulantly when they, well, had someone's prick inside them.

Sherlock remains quiet for a moment, gears turning in his head as his hips piston. At length, he lifts John's leg so it rests on his shoulder.

Then he _licks_ the back of John's kneecap and purrs, "John, your popliteal fossa tastes delightful."

John stares at him, open-mouthed, for a long minute and then bursts into laughter.

Sherlock chokes on his own breath. "Oh, God, John. Don't laugh while I'm inside you."

John grins up at him. "Serves you right. Delightful," he says with affection. He gasps as Sherlock begins licking and kissing his way down John's calf.

"I think," Sherlock says after sucking on a spot just above John's ankle, "I think it's time for me to test some theories."

"Oh, oh, God, you have theories," John moans.

"Of course I do," Sherlock says. Then he runs his thumb down John's arch, and John _writhes_ against Sherlock.

Sarah has _no_ idea where Sherlock has picked up this bit of data. It certainly wasn't from watching them because she can hardly stand looking at feet, let alone touching them.

And normally Sarah would gag at the thought of Sherlock _sucking_ on John's toe, but John makes such an unholy, unprecedented moan that she wonders if she might have to reconsider her stance on feet.

"Fuck, Sherlock. Oh, God... that's... Oh, God. I had no idea..."

"Did you like that, John? How hard do you think you would come if Sarah sucked you off while I did this?" Sherlock asks as he looks at her, his eyes half-closed.

John's fingers are threatening to gouge holes in the bed sheets. "Hard, Sherlock. So hard."

"All out of creative adjectives now, are you?" Sherlock says, his tone completely devoid of mockery. "Fascinating."

Then Sherlock licks John's arch. "Oh, God. Stop. Come down here, please," John begs, panting.

"What? Why?" Sherlock asks.

John looks lost, caught between twenty different answers. Finally, he settles on, "Leverage is becoming a problem."

Sherlock snorts but lets go of John's leg, and he settles between John's legs again, humming appreciatively when John's heels dig into him.

"Yes," John hisses as he arches into Sherlock's thrust. "Yes, that's much better. God, you weren't moving _enough_ earlier."

John smiles up at Sherlock before he turns to look at Sarah. "This is amazing. You are both amazing. I might die from amazing when it's the three of us together again," John says as he reaches out to lace his fingers through hers.

"I'll take that under advisement," Sarah answers, grinning widely.

Sherlock chuckles, but the joke is soon forgotten when he and John settle into the perfect balance of pushing and pulling.

They're getting closer, both of them, and when Sherlock reaches down to stroke John's cock, John abandons his commentary for the soft cadence of grunts that mean he's minutes from coming. He closes his eyes in an attempt to hang on just a bit longer. Sherlock is grimacing now, clearly fighting for control.

Sarah's eyes begin to sting because she _cannot_ blink, cannot look away.

Sherlock's chest is shimmering with sweat now, and his hips are slamming against the backs of John's thighs.

Sarah watches as John's eyes flutter open, and he looks at Sherlock. She _knows_ that look, and when it's directed at her it always makes her heart flip. But seeing John give Sherlock that look... Her heart swells up _again_ , and the last bits of infinitesimal doubt evaporate. This relationship of theirs is going to work despite whatever differences and decisions they still need to settle.

Sherlock presses forward to kiss John again, and they moan into one another's mouths. Then John wrenches away from Sherlock, throwing his head back as he arches. His eyes screw shut and he groans as he comes.

Sherlock follows shortly after, shouting before he collapses on John, his body heaving. They're a tangled, panting mess of sweaty limbs, and Sarah descends from her mountain of pillows so she can kiss them. She threads her fingers through the damp curls on Sherlock's neck and pulls him towards her. The kiss is all warmth and laziness: all the hunger and lust and passion has dissipated, evaporated.

He pulls away from her, his eyes sweeping across her features like he's finally put together all the pieces. It really ought to be terrifying, that particular brand of scrutiny. And yet it isn't.

She kisses him again, and then Sherlock moves out from between John's legs and stands next to the bed, picking up the flannel he'd set on the bedside table earlier and wetting it with water from someone's forgotten dinner glass. He passes it to John and stands awkwardly by the side of the bed while John cleans up.

When Sherlock takes the flannel to the bathroom, Sarah pulls John into her arms. "I love you," she murmurs before kissing him, something that's nearly impossible because she's grinning so widely. John's smiling back when she pulls away.

"You two are beautiful together," she says.

John scoffs. "Not beautiful enough, apparently. Couldn't tempt you to join us."

She splutters and is about to argue when John adds, "I'm just teasing. Sherlock was rather... thorough with you earlier."

Sarah snorts at this and leans in to kiss him again. "Happy?" she asks.

"Very. And you?"

"Ecstatic," she says with a smile that's already beginning to ache. It feels like she's been grinning for hours.

Sherlock leaves the bathroom and studies the bed for a moment. Sarah pats the mattress next to her, and with the slightest of smiles, he crawls into bed next to her.

She wraps an arm around him, pulling him closer to her. Sherlock doesn't _seem_ like a cuddler, but she's certainly not going to leave him on the other hemisphere of the bed to languish by himself. "Is this all right?" she asks.

"Yes," he answers, and she can hear sleep already beginning to seep into his voice.

Her fingers are splayed across Sherlock's chest, her nose buried in the nape of his neck. And John is pressed behind her, his arm reaching across her to rest on Sherlock's hip.

This... this is perfect.

She feels Sherlock's chest rise and fall under her hand and notices how relaxed he is against her, his posture so much more at ease than when he held her, only hours ago. He seems calm, as though, for once, his brain is not cantering around at top speed, hurling itself towards solving the latest case or slamming against the slow points in between.

She's completely aware that this evening, this beginning to their relationship, is atypical. They've taken Sherlock out of his natural habitat by bringing him to the hotel. Once they're back at Baker Street, navigating around two work schedules and unpredictable cases, there will be friction and challenges. There will be kidnappings and near misses and hits and cranky detectives and exasperated flatmates and late nights and Sarah waiting up for them to come home.

Life will move very, very quickly again when they're back at Baker Street. But now, now it is quiet, just the sound of one another breathing.

She sighs. She knows what she would say if it were John in her arms, John who'd lobotomised her earlier with his tongue and fingers, and she's caught, wanting to tell Sherlock. But... no. It's too soon. Too fragile.

And she _must_ have been lobotomised because she has completely forgotten exactly who it is that she's wrapped around.

"Go ahead," he says, "Your fingers keep tensing against my chest like you want to say something. And whatever you've got to say can't possibly be worth the amount of brain power you're expending on _not_ saying it."

She closes her eyes and smiles. He is so... still very much himself, even while naked and in her arms. Not that he wouldn't be. But it's somehow reassuring that things have not changed entirely after the night's events.

She presses a kiss to his head again and swallows, fumbling for courage she doesn't have.

"Sherlock," she begins, stalling with another deep breath, "I love you."

He twists in her arms and jerks his head around to look at her, his eyes wide open and searching.

None of them are breathing now. This moment, this thing that she's said has temporarily frozen time.

After an eternity of silence, Sherlock relaxes and rolls over, pulling her hand back to his chest.

She feels John exhale, but they are both still tense, still waiting for Sherlock to respond. Surely he'll have some response.

He takes a deep breath that she feels against her chest and under her fingers, and she braces for whatever it is he's going to say.

"Charlie."

**Notes for the Chapter:**

> I absolutely could not have posted this without the help of Annietalbot, Christev, Machshefa, Red_Adam, and Sc010f. Your help and insight has been invaluable.
> 
> I also couldn't have written without the help of Wikipedia's handy guides to [semaphore](http://en.wikipedia.org/wiki/Flag_semaphore) and the [International Maritime Letters](http://en.wikipedia.org/wiki/International_maritime_signal_flags#Letters). I had way too much fun contemplating chapter titles as I was writing this.
> 
> Thanks to everyone who kudo'ed and reviewed. It's been a blast posting this. :D


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